Abstract:
A crop harvesting machine is equipped with a crop intake arrangement which delivers crop to a crop processing arrangement. In order to maintain a substantially constant flow of crop to the crop processing arrangement despite a variance in the amount of crop located in various locations on a field, a control circuit employing non-precise or fuzzy logic controls the forward propulsion speed of the harvesting machine and/or the speed of a conveyor used to unload a buffer or crop accumulator that is mounted upstream from the crop processing arrangement. This control is based on crop flow data obtained by a sensor that senses the rate and/or the amount of a crop taken up by the crop intake arrangement, and by a fill sensor associated with a buffer which temporarily accumulates crop at a location upstream from the crop processing arrangement.

Description:
The invention concerns an arrangement for the control of the forward propulsion speed of a harvesting machine. 
     BACKGROUND OF THE INVENTION 
     Various control arrangements are known from the state of the art with which the forward propulsion speed or the intake velocity of an intake arrangement of a harvesting machine can be controlled. 
     EP-377163 A reveals a control arrangement of a harvesting machine in which the intake arrangement is driven at a speed that is proportional to the forward propulsion speed, where the proportionality factor is a function of the type of the particular intake arrangement. DE-19509496 A proposes that the rotational speed of the reel of a combine be controlled as a function of the forward propulsion speed according to a non-proportional characteristic, that is stored in a memory, which produces a higher speed advance for the reel at lower forward propulsion speed and a lower or smaller speed advance for the reel at higher forward propulsion speed. According to EP-812530 A, the rotational speed of the reel can also be a function of the height of the cut. 
     DE-2915531-A describes a harvesting machine in which the forward propulsion speed is controlled in such a way that a constant density of the grain loss material delivered by the harvesting machine results. Similarly, DE-2753813 A proposes the measurement of load changes in cutter, conveyor, threshing or separating arrangements of the combine and to use these for the control of the forward propulsion speed; the aforementioned load should remain constant. DE-2436072-A discloses a harvesting machine in which the forward part of the cutter head is provided with one or more touch sensor arrangements, which detect the amount of the crop to be processed and control the forward propulsion speed of the harvesting machine. According to DE-4320977-A, the measured grain separation at the thresher stator and the measured grain separation at a sieve of the separating arrangement are used to control the forward propulsion speed of a combine, which are used as a function of time. 
     DE-1582177-A reveals a combine in which the conveying speed of the intake arrangement is controlled as a function of the forward propulsion speed in such a way that a constant throughput of the crop is attained. IN GB-2155666-A, the forward propulsion speed is varied so that the rotational speed or the torque of a chopper drum remains constant. 
     U.S. Pat. No. 4,487,002 describes a combine that is provided with a sensor for the throughput of harvested crop, which measures the power applied to the slope conveyor. In addition, the rotational speed of the engine and the forward propulsion speed is measured. These measured values are transmitted to a control circuit that controls the forward propulsion speed and attempts to hold the engine at a constant controllable speed. If the load on the conveyor increases due to harvested crop beyond a threshold value, the actual forward propulsion speed is controlled primarily as a function of the rotational speed of the engine, so as to maintain the desired rotational speed. In case that the load does not increase above this threshold value, that is, no harvesting is performed, but operation on a road is performed, the actual forward propulsion speed is primarily a function of the selected vehicle speed. The combine is braked rapidly when a second threshold value of the throughput is exceeded, that is when a blockage is threatened. 
     Therefore, it is desirable that the forward propulsion speed of the harvesting machine is controlled in such a way that the power output of the engine or the rate at which the crop is processed remains approximately constant. Such a method of operation is particularly economical. 
     However the density or the height of the crop varies on occasion so sharply that the known control arrangements result in sudden jumps or frequent corrections to the speed. Upon sudden increases in the torque due to local increases in the density of the crop, the rotational speed of the engine drops and is followed by a correction in the forward propulsion speed. The result is that less crop is conveyed into the machine for a brief period and thereby the torque of the crop processing arrangement can again return to normal. From its torque reserve, the engine can again return to its original operating rotational speed by briefly increased fuel consumption. Her the increased fuel consumption as well as the mechanical loads on the driveline and torque transmitting components due to load fluctuations can be seen as detrimental. In addition, the continuing acceleration and retarding processes are uncomfortable for an operator sitting on the machine. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a harvesting machine for taking up and processing crop and including controls which overcome the drawbacks of the prior art. 
     An object of the invention is to provide a harvesting machine having controls that take into account the non-linear character of the conveying of crop into the machine to be processed so that the main drive engine of the machine is operated at a constant load. 
     A more specific object of the invention is to provide a harvesting machine, as set forth in the immediately preceding object, wherein sensors are provided for determining the rate and/or the amount of crop taken up by a crop intake arrangement and to control the forward propulsion speed of the machine by using a fuzzy logic controller in such a way that the rate that crop is processed by a crop processing arrangement of the harvesting machine, for example the chopper drum of a forage harvester, or a cutter head arrangement, conveyor arrangement, thresher arrangement or separator arrangement of a combine corresponds to a target value. For the control of the forward propulsion speed a hydrostatic drive is used which incorporates a hydrostatic pump having a swashplate which may be controlled electronically either directly or through a servo motor. 
     Yet another object of the invention is to provide a harvesting machine, as set forth in the immediately preceding object, wherein the machine is also controlled so that the throughput reaches an optimum for each point in time, and that the machine can always operate close to the power limit, even under varying harvesting conditions. This is accomplished by using a control arrangement in which the optimum engine speed is pre-selected for effecting a desired throughput, with fuzzy logic being used to generate membership or associative functions for the input variable(s) of the control circuit and determines output values from a controller with which the forward propulsion speed is controlled. 
     Still another object of the invention is to provide a harvesting machine, as set forth in the immediately preceding object, wherein the control arrangement includes a control including fuzzy logic for varying the speed with which crop is conveyed to a crop processor. A further refinement of this object is to equip the harvesting machine with a crop accumulator or buffer located upstream from the crop processor and from which crop may be dispensed by a variable speed screw conveyor so as to maintain a steady flow of crop to the crop processor, with the flow of crop being monitored by measuring the thickness of the mat of crop by continuously measuring the distance between a pair of feed rolls provided downstream of the buffer and upstream of the crop processor, the buffer being operational to equalize short and medium term fluctuations in the rate of the crop taken up. The fill level of the buffer can also be detected by means of a sensor, whose output signal is transmitted to a control circuit, that controls the forward propulsion speed of the harvesting machine and/or the speed of the conveyor in such a way that a threshold value of the fill level of the crop in the buffer is reached as much as possible without under running. This control circuit is, in particular, the fuzzy logic controller described above, but may also be a non-fuzzy logic. As an alternative to the signal from the fill sensor, a deviation between the signal and a signal that corresponds to a predetermined fill level, can be transmitted to the fuzzy logic controller. The time differential of the signal or of the aforementioned deviation, which however, are identical, since the predetermined fill level is constant, can also be transmitted to the fuzzy logic controller. The variable speed of the conveyor may be accomplished by a hydrostatic drive including a hydrostatic pump having a swashplate which may be controlled electronically either directly or through a servo motor. 
     These and other objects will become apparent from a reading of the ensuing description together with the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic left side view of a harvesting machine. 
     FIG. 2 is a schematic vertical longitudinal sectional view taken through a harvesting machine having a front harvesting attachment. 
     FIG. 3 shows a vertical section through the screw conveyor of FIG.  2 . 
     FIG. 4 is a top view of the screw conveyor of FIG.  2 . 
     FIG. 5 a block diagram of a control system of the harvesting machine. 
     FIG. 6 is a program sequence of the control system. 
     FIG. 7 is a graph showing an membership function for the spacing between feed rolls. 
     FIG. 8 is a graph showing an membership function for the fill level of a buffer. 
     FIG. 9 is a graph showing the angle adjustment for the propulsion drive. 
     FIG. 10 is a graph showing the angle adjustment for the drive of the screw conveyor. 
     FIG. 11 is a schematic left side view of a harvesting machine according to a second embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A first embodiment of a harvesting machine  10  is in the form of a self-propelled forage harvester supported on a frame  12  that is carried by front and rear wheels  14  and  16 . The operation of the harvesting machine  10  is performed from an operators cab  18  from which a crop intake arrangement, not shown in FIG. 1, may be viewed while being controlled. Crop taken up from the ground by means of the crop intake arrangement, for example, corn, grass or the like, is conducted to a chopper drum  22  which chops it into small pieces and transmits it to a conveyor arrangement  24 . The crop leaves the harvesting machine  10  to an accompanying trailer through a discharge duct  26  which may be pivoted about an upright axis. Between the chopper drum  22  and the conveyor arrangement  24  a post-chopper reducing arrangement  28  extends, through which the conveyed crop is conducted tangentially to the conveyor arrangement  24 . 
     Referring now to FIG. 2, there is shown a crop intake arrangement  20 , that may, for example, be a pick-up known in itself, a mower-chopper, picker or front mower attachment, that takes up crop from the ground, or cuts it off, and conducts it to a conveyor belt  30  that is driven. The crop is brought by the conveyor belt  30  into a buffer  32 , that is used for temporary storage of the crop before further processing. In some types of front harvesting attachments, for example, mower-choppers or pickers, the conveyor belt  30  can be eliminated and the crop may be conveyed from the front harvesting attachment  20  directly into the buffer  32 . A screw conveyor  34  is arranged at the bottom of the buffer  32 , which successively takes crop out of the buffer  32  and conducts it to two pairs of pre-compression rolls  36  arranged such that one pair is behind the other. The pre-compression rolls  36  convey the crop to the chopper drum  22  which chops it and conducts it through the post-chopper reduction arrangement  28  and the conveyor arrangement  24 , and then through the discharge duct  26  to the accompanying trailer. A main engine  38 , that usually is an internal combustion engine (Diesel engine), drives the individual arrangements with which the crop is transported and processed. For forward propulsion of the harvesting machine  10 , a hydrostatic propulsion drive  40  is arranged at the front wheels  14 , the drive is loaded with pressurized hydraulic oil from an oil pump, not shown, driven by the man engine  38 . The forward propulsion speed attained by the propulsion drive  40  of the harvesting machine  10  is variable, which is performed in a manner known in itself by means of a swash plate in the propulsion drive  40  or by variation in the oil pressure, with which the propulsion drive is loaded. The screw conveyor  34  is also provided with a hydrostatic drive  42 , whose speed can be varied. The buffer  32  with the screw conveyor  34  can be rigidly mounted on the harvesting machine  10 , where the front harvesting attachment  20  (and, if necessary, the conveyor belt  30 ) is then preferably fastened to the harvesting machine  10  so as to be removable. As an alternative, the buffer  32  with the screw conveyor  34  is connected (permanently or so as to be removable) to the front harvesting attachment  20  attached to the harvesting machine  10  so as to be removable. The last named solution has the advantage that it can be applied to existing harvesting machines that are not equipped with a buffer  32 . 
     A number of sensors are provided for the control of the harvesting machine  10 . A rotational speed sensor  44  measures the rotational speed of the screw conveyor  34 . A fill level sensor  46  detects the fill level of the buffer  32  with harvested crop. A roll spacing sensor  48  measures the spacing between two interacting pre-compression rolls  36 ; this distance is a measurement of the amount of crop conducted to the chopper drum  22 , which additionally is a function of the rotational speed of the pre-compression rolls  36 , which can also be measured or adjusted. Such a sensor is known from U.S. Pat. No. 5,795,221, granted to Diekhans on Aug. 18, 1998. A further rotational speed sensor  50  measures the rotational speed of the chopper drum  22 , which is driven directly mechanically by the main engine  38  or hydraulically by means of a hydrostatic drive. Furthermore, the rotational speed of the main engine  38  is measured by a rotational speed sensor  52  and a forward propulsion speed sensor  54  measures the forward propulsion speed of the front wheel  14 , which corresponds to that of the harvesting machine  10 . All the aforementioned sensors are connected over so-called CAN bus with a control circuit  56 , which is shown in FIG.  5 . 
     The screw conveyor  34  is shown in greater detail in FIGS. 3 and 4. The screw conveyor  34  conveys harvested crop in the direction of the arrow  58  out of the buffer  32  and conducts it to the pre-compression rolls  36 . As can be seen from FIG. 4, the harvested crop is conveyed by the screw conveyor  34  axially with respect to the forward propulsion direction of the harvesting machine  10  from left and right to the output region in the lower region of the buffer  32  The output region is compartmentalized by a cover  60  from harvested material in the butter  32  lying above it. The output region of the screw conveyor  34  is configured as a so-called centrifugal conveyor, which conveys harvested material in the direction of the arrow  58  radially from the screw conveyor  34  into the pre-compression roll channel of the harvesting machine  10 . Since the screw conveyor  34  naturally conveys a relatively constant mass flow, various rates of throughput can be obtained by varying the rotational speed of the screw conveyor  34 . The improvement over commercially available front harvesting attachments for taking up and conveying harvested crop, for example, grass, lies in the controllable and continuous conveying performance of the screw conveyor  34 . 
     FIG. 5 shows a block diagram of the control system with the control circuit  56  that can be configured as a microprocessor or controller with corresponding control software. The control circuit  56  is a fuzzy logic controller (non-precise logic), which is supplied with two process values as input values. On the one hand, these input values are the differential between a pre-set spacing between the pre-compression rolls  36 , and the actual spacing, measured by means of roll spacing sensor  48  between the pre-compression rolls  36 , and, on the other hand, the difference between a pre-determined target fill level in the buffer  32  and the actual fill level in the buffer  32 , which is measured by means of the sensor  46 . As previously noted, the spacing between the pre-compression rolls  36  is a measure of the mass throughput of the harvesting machine  10 , that is, the volume of harvested crop processed per unit of time. The desired throughput can be firmly pre-set or can be provided as input by a user; this target spacing is transmitted to an input connection  62  of the control circuit  56 . The target fill level in the buffer  32  can also be provided by the operator of the harvesting machine as input or permanently pre-set at an appropriate value; it is transmitted to the control circuit  56  as an input connection  64 . The control circuit  56  has two outputs, specifically a rotational speed adjusting signal that predetermines the rotational speed of the screw conveyor  34 , shown in the drawing as a constant conveyor, and a propulsion speed adjusting signal, with which the speed of the hydrostatic drive  40  of the wheel  14  is controlled. Thereby the control circuit  56  controls the rotational speed of the screw conveyor  34  and the forward propulsion speed of the harvesting machine  10 . 
     The rectangle shown at the right in FIG. 5 indicates a process  66  that reproduces the taking up and processing of the harvested crop with the application of buffer  32 , main engine  38  and forward propulsion drive  40 . Initial values of this process are the forward propulsion speed measured with the forward propulsion speed sensor  54 , the rotational speed of the screw conveyor  34  measured with the rotational speed sensor  44 , the rotational speed of the main engine  38  measured with the rotational speed sensor  52 , the rotational speed of the chopper drum  22  measured with the rotational speed sensor  50 , as well as the fill level of the buffer  32  measured with the sensor  42  and the spacing between the compression rolls  36  measured with the roll spacing sensor  48 . The latter can also be used for measurement of the yield and for recording. The measured values of all six aforementioned sensors are transmitted to the control circuit  56 . 
     The control circuit  56  contains a so-called fuzzy logic controller that is composed of the partial systems fuzzification  68 , inference  70 , control net work  72 , and defuzzification  74 . Following is the method of operation of the control circuit  56 . From the process  66  to be controlled, the fuzzy logic controller is supplied with system magnitudes (process magnitudes) as initial magnitudes. These are exact (precise) signals discrete in time, that the fuzzy logic controller cannot yet understand in view of its non-precise logic. Therefore, in the first step (fuzzification  68 ) a fuzzification of the precise process magnitudes is undertaken by the fuzzy logic controller,  56 , in that by the use of membership functions an index number is associated with each initial magnitude, that defines a measure for the association of the immediate actual combination of values of the initial magnitudes to various non-precise amounts (fuzzy sets). In that way, it can happen that one or more precise initial magnitudes(s) with various membership factors can be associated with several fuzzy sets, where for a number the degree of association can be greater than for another. The definition of the membership functions can be performed heuristically or based on a model. 
     The core of the control is composed of “if-then” rules. The “if” part (condition part) of the rules consists of the logical linkage of fuzzy sets, which are linguistic, non-precise circumscriptions of amounts, that ascribe certain characteristics to the initial magnitudes. The “then” part (consequence) consists of a non-precise, linguistic circumscription how the output magnitudes of the controller should be shaped on the basis of the characteristics of the input magnitudes. Therefore the rule base  72  is a linguistic non-precise description of expert knowledge on the basis of which the controller makes its decisions, which adjusting magnitude it transmits to the process  66 . 
     In the second phase, the inference  70 , the fuzzy logic controller initially determines which condition cases (“if” parts) of the “if-then” rules defined in the rule base, apply to the actual situation at the inputs to the controller (so-called matching). The matching process finds all applicable rules for a certain combination of values of the input magnitudes in that it considers all index numbers for all fuzzy sets of these input magnitudes, that are greater than zero. After the matching process, therefore, a selection has been made as to which rule applies among all the rules of the rule base  72  for the given input magnitude combination. The following step is the actual inference algorithm. In it, an index number for the logical linkage of these fuzzy sets is calculated, that is, for the operating part of the rules in order to quantify the certainty, with which the various condition parts of the rules apply to the particular input magnitude situation. For the inference algorithm itself several operating parts of the rules with various membership factors are available. The inference mechanism  70  applies weighting to the conclusions of the rules that corresponds to the immediate membership factor of the condition part in order to quantify the applicability of various conclusions. It forms the so-called implied fuzzy sets. After this process has been performed for each identified rule, several proposals are available for the controller output magnitudes, to which various weighting factors apply. 
     In the last step, the fuzzy logic controller composes a single conclusion from all weighted proposals for the output magnitude of the controller (final conclusions), which then is applied as controller output magnitude. This step is designated as defuzzification  74  and there are several defuzzification methods, to calculate the controller output magnitude. This output magnitude is again an exact (precise) value that is directly transmitted to the process. 
     The fuzzy logic control algorithm applies only the deviations from the rules and their variations with time as input magnitudes. The remaining input data are required for monitoring and control algorithms, that also run in the control circuit  56  but not in the fuzzy logic controller. They are used to calculate the throughput of harvested crop as well as for the monitoring of the entire harvesting and conveying process. 
     Controller output magnitudes are an adjusting signal for a change in the rotational speed of the screw conveyor  34  as well as an adjusting signal for a change in the propulsion speed of the harvesting machine  10 . Further characteristics of the control system are extensive diagnostic and indicating capabilities as well as a calibrating operating mode and the ability to pre-select a certain mass throughput, that is maintained at a constant level by the control system. 
     The calculation of the controller output magnitudes is performed as explained above, here it should be noted that the controller has four input magnitudes (the difference between target and actual spacing of the compression rolls  36 , its time differential, the difference between target and actual fill level of the butter  32  as well as its time differential) and two output magnitudes. Hence, this is a multiple input multiple output (MIMO) system. A considerably simplified method of operation of the controller can be defined. 
     Specifically, in case the fill level of the buffer  32  has declined below a certain threshold value, the forward propulsion speed of the harvesting machine should be increased until the full level has again reached an adequate value. The fill level of the buffer  32  must be such that the screw  34  is always loaded with material. 
     In case the spacing of the pre-compression rolls  36  deviates from the pre-set value, then the rotational speed of the screw conveyor  34  is changed to conform; that is, it must be increased if the spacing falls below the target spacing and is corrected downward if the spacing increases above the target spacing. 
     A better response of the control system is attained by the inclusion of the changes in time of the deviations from the control value. 
     Referring now to FIG. 6, it can be seen that after the start step S 1 , for example, after the starting of the harvesting machine  10 , the control circuit is initialized in step S 2 , that is, the programs and data required by the control circuit  56  are retrieved from permanent memory. Step S 3  inquires which operator input is currently active. There are three options, namely, manual control, automatic control and calibration. If manual control is selected, step S 4  follows, in which the automatic control system is turned off, and the forward propulsion speed is controlled manually. If calibration is selected, step S 5  follows, in which a calibration and diagnosis of the functions of the control system are performed. If automatic control is selected, step S 6  follows, in which the target values are retrieved, in particular the rate for the particular crop harvested. After that, in step S 7 , the harvesting process is regulated and monitored in the manner described above. Here, step S 8  determines regularly whether a system failure exists. If this is the case, step S 4  follows, that is control is shifted to manual control. Alternatively, if there is no system failure, that is everything is in order, step S 9  follows, in which the actual data are displayed on an indicator arrangement in the operator&#39;s cab  18 . Hence, the operator can read, for example, the forward propulsion speed, and the rate and total amount of crop harvested. Step S 10  follows, which inquires whether a metal detector, arranged in one of the pre-compression rolls  36 , has detected ferromagnetic material. In case metal has been detected, step S 11  follows with the end of the process, since the operator must stop the harvesting machine  10  and remove the metal. Otherwise step S 3  again follows. 
     In the following, the principle of the control circuit  56  with a fuzzy logic controller is explained on the basis of an example. Accordingly, the fuzzification  68  employs the one-dimensional, triangular membership functions for the input magnitudes of the roll spacing and fill level, shown in FIGS. 7 and 8. Five fuzzy sets are provided for the roll spacing, in particular, negative large (NG), negative small (NK), target (SA), positive small (PK) and positive large (PG). Therefore, the range of the values for the roll spacing is subdivided with the membership function shown in FIG. 7 non-precisely into five amounts. For the fill level of the buffer  32 , four fuzzy sets are provided. Specifically critical (K), still adequate (NA), target (SB) and over target (ÜS). The range of values for the fill level has been subdivided non-precisely into four amounts with the membership function shown in FIG.  8 . Two matrices result thereby with a dimension 5×4 for the controller output values in the rule base  72 . 
     The rule base  72  for the two output magnitudes of the controller could result in a matrix P 1  that appears as follows: 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 NG 
                 NK 
                 SV 
                 PK 
                 PG 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 K 
                 θ1 
                 θ1 
                 θ1 
                 θ1 
                 θ1 
               
               
                   
                 NA 
                 θ2 
                 θ2 
                 θ2 
                 θ2 
                 θ2 
               
               
                   
                 SF 
                 θ4 
                 θ4 
                 θ4 
                 θ4 
                 θ4 
               
               
                   
                 ÜS 
                 θ3 
                 θ3 
                 θ3 
                 θ3 
                 θ3 
               
               
                   
                   
               
             
          
         
       
     
     In the above table, the roll spacing values form the columns and the fill level values the rows. The table defines the change in the adjusting angle of the hydraulic pump for the forward propulsion drive  40  as a function of the roll spacing and of the fill level. The meaning of the angle θ is such that at θ1 the adjusting angle of the hydraulic pump for the forward propulsion drive  40  is sharply increased, so that the forward propulsion speed increases sharply. At θ2 the adjusting angle is increased somewhat, at θ3 it is decreased somewhat and at θ4 it remains unchanged. In place of the change of an angle, the adjustment of the forward propulsion speed can be performed in any other desired way. 
     The adjusting signal for the speed of the screw conveyor  34  results in a second matrix P 2 , that defines the change in the adjusting angle for the drive  42  of the screw conveyor  34  as a function of the roll spacing and of the fill level: 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 NG 
                 NK 
                 SV 
                 PK 
                 PG 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 K 
                 Ψ5 
                 Ψ5 
                 Ψ5 
                 Ψ3 
                 Ψ4 
               
               
                   
                 NA 
                 Ψ1 
                 Ψ2 
                 Ψ5 
                 Ψ3 
                 Ψ4 
               
               
                   
                 SF 
                 Ψ1 
                 Ψ2 
                 Ψ5 
                 Ψ3 
                 Ψ4 
               
               
                   
                 ÜS 
                 Ψ1 
                 Ψ2 
                 Ψ5 
                 Ψ3 
                 Ψ3 
               
               
                   
                   
               
             
          
         
       
     
     In this table, the roll spacing also forms the columns and the fill level the rows. The angles Ψ have the meaning, that with Ψ1 the adjusting angle is sharply increased, that is, the conveying speed is sharply increased. With Ψ2, the adjusting angle is increased somewhat, with Ψ3 it is reduced somewhat, with Ψ4 it is reduced sharply and with Ψ5 it remains constant. Here too, the variation of the conveying speed may be performed instead of a variation in the angle, by any other desired means. 
     From the non-precise values of the adjustment magnitudes, two precise adjustment values (controller output values) are determined with the aid of a classical defuzzification method (for example, center of gravity method), which is explained in the following on the basis of a sample pair of values. In case the roll spacing is 4 mm (corresponds to the fuzzy value “too large”) and the fill level of +5% is increasing (“too much”), the corresponding values of the membership functions can be read from FIGS. 7 and 8. 
     For the roll spacing, an association can be found as μ=0.8 for positive small (PK) and μ=0.2 for target value (SV). For the fill level, the result is μ=0.6 for target value (SF) and μ=0.4 for over target value (ÜS). The matching process discovers that the amounts PK, SV, SF, and ÜS apply to the input value situation. Therefore, all rules with the linkage to these amounts in its conditional part find entry into the calculation of the adjustment value. IN the rule base  72 , that is the above matrices, the adjustment values for the forward propulsion speed and the conveyor speed can be read. In each of the two matrices, four target adjustments must be considered. For the individual adjustment values, an membership measure is calculated by the application of the minimum operator “min”, that is, in each case the smaller membership measure is used. For the pair of values PK, SF one finds in matrix P 2  Ψ3, whose membership measure μ for PK amounts to 0.8 and for SF amounts to 0.6 (see FIGS.  7  and  8 ). Therefore, the target value Ψ3 is associated with an membership measure μ=0.6, while for the same pair of values according to matrix P 1  results in θ4. The membership measure μ for θ4 also results in 0.6, calculated with the “min” operator. Analogously, one finds with PK, ÜS, μ=0.4 for θ3 (the minimum of 0.8 and θ4), as well as μ=0.4 for Ψ3 (the minimum of 0.8 and 0.4). With SV, SF there results for θ4 a value for μ=0.2 and for Ψ5 the result is also μ=0.2. With SV, ÜS the result is μ=0.2 for θ3 and μ=0.2 for Ψ5. In case one now obtains for one of the adjustment values various membership measures μ, the maximum is in each case used again, that is with Ψ3 then μ is set equal to 0.6, which is the maximum out of 0.4 and 0.6. As a result, one obtains for Ψ3−μ=0.6, for Ψ5−μ=0.2, for θ3−μ=0.4 and for θ4−μ=0.6. Therefore, one obtains two non-precise adjustment values for each of the two initial magnitudes. With the aid of the membership functions for the initial controller value, the precise output value can be read. For this purpose, a normalizing on one of the membership mass can be performed so that the sum of the normalized μ is equal to 1. Here Ψ produces normalized μ if 0.75 for Ψ3 and 0.25 for Ψ5, here θ results in 0.4 for θ3 and 0.6 for θ4. The normalizing is performed by dividing μ calculated above by the sum of the μ for θ or Ψ. Finally, the controller output magnitude can be read from FIG. 9 or  10 . For this example, the result is an angle of −2.8° for the forward propulsion speed and −4.5° for the conveyor speed. 
     FIG. 11 shows the harvesting machine  10  in the form of a forage harvester according to a second embodiment of the invention. Components that correspond to components of the first embodiment are identified with the same reference numerals. In the second embodiment, a crop intake arrangement  20  in the form of a pick-up is provided which contains a pair of rolls  82 ,  84  extending transverse to the direction of forward propulsion for the acceptance from the ground of crop already mowed. The crop is conducted to a screw conveyor  34  that is driven with variable rotational speed by a hydrostatic drive  42  and that conducts the crop from the rolls  82 ,  84  to the pre-compression rolls  36 . Therefore, there is only a relatively small volume available for a buffer  32  underneath the screw conveyor  34 . The control circuit  56  is provided with the following input signals: Rotational speed of the main engine by means of the sensor  52 , forward propulsion speed by means of the sensor  54 , rotational speed of the screw conveyor  34  by the rotational speed sensor  44  and torque of the drive for the screw conveyor  34  by means of a torque sensor  80 . /The control circuit  56  is also provided with a fuzzy logic controller, which generates output values with which the forward propulsion speed of the harvesting machine  10  is controlled by means of the hydrostatic propulsion drive  40 . In addition, the conveying speed of the screw conveyor  34  is controlled by means of the fuzzy logic controller, which uses the hydrostatic drive  42  with variable rotational speed. The input values for the fuzzy logic controller are the drive torque of the screw conveyor  34  and the rotational speed of the screw conveyor  34 , as well as their time differentials. The drive torque for the screw conveyor  34  contains data as to the fill level, since the screw conveyor  34  must be driven with greater power when the fill level is high than at a low fill level. Her it could also be appropriate to provide a sensor for the fill level of the buffer  32  and to connect it to the control circuit  56 , as in the first embodiment.