Patent Publication Number: US-11035314-B2

Title: Machine control system

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a machine control system. 
     2. Description of Related Art 
     Regional energy independence has been recommended in Europe and the United States, and there is a transitional movement to biomass power generation using an agricultural waste or the like, solar power generation, and wind power generation. Since biomass fuels are obtained in association with human economic activity, the availability thereof varies depending on the location and the time. Therefore, it is assumed to use a plurality of types of fuel in a combined manner, and an engine control for power generation coping therewith is required. 
     In the related art, a control map of multiple control command values including the ignition timing and the air-fuel ratio is manually created for each fuel, and the engine is feedforward-controlled. However, if the engine is controlled by the combination of the plurality of types of fuel, it is complicate to manually create a control map for each of expected combinations of plural fuels and the mixing ratio thereof, and it is difficult to have practical usage due to a high cost. 
     In this case, the machine learning is also considerable by modeling the engine. There is a technique of detecting an abnormal state of a system by repeatedly applying and removing a kernel to and from a regression model to refine the regression model. For example, the technique is described in U.S. Pat. No. 7,844,558. 
     In addition, there is a technique of obtaining an optimum operating condition using linear programming when a regression model of the operation state and the operation index of a plant is linear or using quadratic programming when the regression model are non-linear. For example, the technique is described in JP-A-2012-074007. 
     In the technique described in U.S. Pat. No. 7,844,558, replacing and adding the learning data or the kernel result in improvement in accuracy of abnormality determination while operating the target device. However, when a machine such as an engine is controlled, there is also a possibility that the newly obtained learning data does not necessarily include data that satisfies a specific condition from the beginning, and sufficient accuracy cannot be obtained for a specific condition. 
     In the technique described in JP-A-2012-074007, a regression model under the whole operating conditions of the plant is created to optimize the operating condition, thereby calculating the optimum operating condition. However, when a machine such as an engine is controlled, it is difficult to create a large number of learning models in advance for practical use. 
     SUMMARY OF THE INVENTION 
     According to the above, an object of the present invention is to obtain a command value that satisfies a specific condition even when a small number of learning models is used in controlling of a machine such as an engine. 
     In the invention, an outline of exemplary embodiments will be briefly described as follows. A machine control system includes: a selecting unit which acquires a state quantity of a machine converted from data acquired by a sensor provided in the machine to select two or more learning models according to the acquired state quantity; a composing unit which inputs the state quantity acquired by the selecting unit to each of the two or more learning models selected by the selecting unit to calculate a composed value using a command value output from each of the learning models; and a learning unit which outputs a command value with respect to the machine in a range based on the composed value calculated by the composing unit, acquires a state quantity of the machine, searches for a command value of a specific condition from a combination of the output command value and the acquired state quantity, and outputs the searched command value to the machine, thereby creating a new learning model. 
     According to the invention, it is possible to obtain a command value satisfying a specific condition by only using a small number of learning models in controlling of a machine such as an engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration example of an engine system including composition of outputs of learning models; 
         FIG. 2  is a diagram illustrating an example of a process flowchart according to a first embodiment; 
         FIG. 3  is a diagram illustrating a configuration example of an engine system including calibration; 
         FIG. 4A  is a diagram illustrating an example of a process flowchart according to a second embodiment; 
         FIG. 4B  is a diagram illustrating the example of the process flowchart according to the second embodiment; 
         FIG. 5  is a diagram illustrating an example of a process flowchart according to a third embodiment; and 
         FIG. 6  is a diagram illustrating an example of a process flowchart according to a fourth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments will be described with reference to the drawings. In  FIGS. 1 to 6  for describing the embodiments, the corresponding elements having the same function are given the same reference numerals, and the repetitive description thereof will be omitted. 
     First Embodiment 
       FIG. 1  is a diagram illustrating a configuration example of an engine system according to a first embodiment. The engine system includes an engine  101 , an observation device  102 , a controller  103 , a PC  104  (engine control device), and a data server  105 . 
     The observation device  102  acquires raw data from a sensor provided in the engine  101 , converts the data into an engine condition index indicating the combustion state of the engine  101 , and outputs the index to the PC  104 . The controller  103  converts an engine command value acquired from the PC  104  into a command signal and outputs the signal to the engine  101 . The observation device  102  may include an analog-to-digital converter, and the controller  103  may include a digital-to-analog converter. 
     In the data server  105 , a learning model and a label thereof are stored, the learning model including an engine condition index as an input and an engine command value as an output. The learning model is created for each operating condition of the engine  101 . The learning model may include a combination of an engine index and a target index as an input. 
     Here, the label is a representative value of the engine condition indices of a data set used to create the learning model. The target index is an index as a target to which the engine condition index is to be closer by changing the engine command value to change the engine condition index, and is input from the outside of the PC  104 . 
     The PC  104  includes a learning model selecting unit  106 , a composing unit  107 , and a learning unit  108 . Based on the engine condition index input from the observation device  102 , the learning model selecting unit  106  selects and acquires a group of base learning models which is learning models to be used in the learning unit  108  among the learning models stored in the data server  105 . 
     The composing unit  107  composes the output values of the group of base learning models. The learning unit  108  searches for an engine command value with the maximum thermal efficiency in the peripheral region of the output value composed by the composing unit  107 , outputs the engine command value to the controller  103 , generates a learning model, and stores the learning model in the data server  105 . 
     The PC  104  is a computer including a processor  121 , a storage unit  122 , and an input/output unit  123 . The storage unit  122  may include a memory or a secondary storage device, and the input/output unit  123  may include a serial interface, a parallel interface, or a network interface. 
     One or more of the learning model selecting unit  106 , the composing unit  107 , and the learning unit  108  may be implemented by a dedicated circuit or may be implemented by the processor  121  that executes a program stored in the storage unit  122 . 
       FIG. 2  is a diagram illustrating an example of a process flowchart of the engine system in this embodiment. In step  201 , the observation device  102  acquires raw data of the sensor provided in the engine  101  for one control cycle. 
     For example, a pressure sensor for detecting the in-cylinder pressure of the engine  101  is used as the sensor. The maximum value of the raw data of the pressure sensor for one control cycle is output to the PC  104  as an engine condition index. In one control cycle, four strokes including intake, compression, explosion, and exhaust of the engine may be set as one cycle. 
     The sensor is not necessarily a pressure sensor, but may be any sensor, such as a strain sensor, a microphone, a temperature sensor, a flowmeter for fuel or air, an encoder that detects the engine speed, or a torque sensor that detects the axial torque of the engine  101  as long as it detects the combustion state of the engine  101 . A plurality of sensors may be provided in the engine  101 , and a plurality of raw data of the plurality of sensors may be acquired. 
     The engine condition index is not necessarily the maximum value of the raw data of the pressure sensor, and may be, for example, a combination of a plurality of raw data of the pressure sensor or a combination of the raw data of the pressure sensor and a value acquired from another sensor, as long as the value corresponds to the type of data of the engine condition index to be input to the learning model stored in the data server  105 . Alternatively, the learning model to be acquired in step  202  may be selected according to the type of data of the engine condition index acquired in step  201 . 
     In step  202 , the learning model selecting unit  106  acquires the group of base learning models from the data server  105 . That is, two or more learning models are acquired as the group of base learning models in ascending order of the distance between the engine condition index output from the observation device  102  in step  201  and the engine condition index of the label for the plurality of learning models stored in the data server  105 . 
     Part of the plurality of engine condition indices acquired in step  201  may be used in step  202 . Also, not only the engine condition index, but also a target index such as the required torque (required pressure), or a combination of the engine condition index and the target index may be used in step  202 . 
     Further, a plurality of learning models stored in the data server  105  may be acquired at any conditions instead of being based on the distance between the engine condition index output from the observation device  102  and the engine condition index of the label for the plurality of learning models. 
     The distance between the engine condition indices may be a distance calculated from a plurality of values of a plurality of engine condition indices of the same type according to a preset calculation formula. In addition, the distance between the engine condition indices may be a distance calculated by multiplying a weight to a plurality of values of a plurality of different types of engine condition indices according to a preset calculation formula, the weight being set in advance for a combination of the plurality of different types of engine condition indices. 
     In step  203 , the composing unit  107  inputs the engine condition index acquired in step  201  to each base learning model acquired in step  202  to acquire respective output values. In step  204 , the composing unit  107  composes the output values of the respective base learning models. 
     The calculation of the composing of the output values is, for example, a calculation of the weighted average value using a composition weight set for each base learning model. For the composition weight, the characteristic ratio is used which is obtained from the engine condition indices of the data set used for creating each base learning model. 
     For example, when the base learning models are two models A and B, and the ratio (characteristic ratio) of the in-cylinder pressure maximum value of the data set used for creation is A:B=3:2, the composition weight W(A) of the model A is three and the composition weight W(B) of the model B is two. However, the characteristic ratio is not limited to the ratio of the in-cylinder pressure maximum value, but may be a ratio obtained from an engine condition index such as a ratio of an engine torque. 
     Assuming that the value of the engine condition index of the model A is S(A), the value of the engine condition index of the model B is S(B), the output value of the model A is O(A), the output value of the model B is O(B), and the value of the engine condition index in the current control cycle is S(T), the weighted average value AVE is calculated as follows. 
     
       
         
           
             
               
                 
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     However, the calculation of the weighted average value is not limited to the expression above. 
     Further, the output value obtained by the composition is not limited to the weighted average value, but may be an average value without being weighted or a value obtained by correcting an average value or a weighted average value with an engine condition index or the like. Alternatively, an average value of parameters of the base learning models or the like may be used to create a new learning model, and an engine condition index may be input to the learning model to calculate an output value. 
     In step  205 , the learning unit  108  sets a search range based on the output value composed in step  204 . The search range is set with the output value calculated in step  204  as the center value so that the search range has a preset search width. The output value calculated in step  204  is not necessarily the center value, and the search range may be set with the output value calculated in step  204  as the boundary value. 
     The search width is not necessarily fixed to the preset search width, and a table or calculation formula for setting the search width based on the output value calculated in step  204  or the engine condition index may be set in advance. 
     Further, the search increment may be set in advance. Alternatively, the search increment is not necessarily fixed to the preset search increment, and a table or a calculation formula for setting the search increment based on the output value calculated in step  204  or the engine condition index may be set in advance. 
     In step  206 , the learning unit  108  sequentially outputs the engine command value determined from the search range set in step  205  and the search with the search increment set in advance to the controller  103 , and the controller  103  converts the value into a command signal to output the signal to the engine  101 . That is, a plurality of engine command values are sequentially determined and output while shifting the engine command value by the search increment from the boundary value (the value at the end of the range) of the search range. 
     As a result, the engine command values are output as many as the number by which the search width is divided by the search increment in step  206 . The value to be output to the controller  103  is not necessarily the engine command value determined from the search range and the search increment, but may be a value obtained by adding noise to the engine command value. 
     Since one determined engine command value is output a plurality of times and noise is added to each output, an engine command value is output which cannot be determined only from the search increment due to the assignment of the same engine command value. In addition, there is a possibility that shifting may occur in the combustion state of the engine  101 , so that the same engine command value may be output a plurality of times regardless of the addition of noise. 
     The engine command value may be a value of commanding to control one or both of the ignition timing and the air-fuel ratio of the engine  101 . The value of commanding to control the air-fuel ratio may include a value of the injection start timing and the injection timing of the fuel, or a value of the injection amount of the fuel. The engine command value is not limited to these values, but may be any value as long as the value used for controlling the combustion state of the engine  101 . 
     In step  206 , the learning unit  108  further is input with the state of the engine  101  with respect to the output engine command value from the observation device  102  as an engine condition index. In step  207 , the learning unit  108  stores a combination of the plurality of engine command values output to the controller  103  and the plurality of engine condition indices input from the observation device  102  in the data server  105  as a data set for searching. 
     In step  208 , the learning unit  108  searches for the engine command value with the maximum thermal efficiency from the data set for searching stored in step  207 . When the engine command value with the maximum thermal efficiency is found by searching, the learning unit  108  may repeatedly perform the process of setting a new search range based on the found engine command value to search for a new engine command value and storing the data set for searching in the data server  105  to search for an engine command value with the maximum thermal efficiency. 
     The process for finding the engine command value with the maximum thermal efficiency is not limited to the above process in which the search range and the search increment are preset and the searching is repeatedly performed. In this process, for example, the search may be repeatedly performed while gradually decreasing the search increment. 
     In this process, in order to reduce the number of pieces of data to be searched for, the search range may be narrowed down by estimating the occurrence probability distribution as the data of the engine command value with the maximum thermal efficiency, a reinforcement learning may be introduced to the searching, or the margin of the operating condition within the search range may be set based on information acquired by any sensor. 
     In step  209 , the learning unit  108  outputs one engine command value with the maximum thermal efficiency to the controller  103  for 1,000 control cycles. The number of output control cycles is not necessarily 1,000, and may be any number as long as it is necessary for creating a learning model. In step  209 , the engine command values may be output by a larger number than the number of outputs when the same engine command value is output a plurality of times in step  206 . 
     In step  209 , the learning unit  108  is further input the state of the engine  101  with respect to the output engine command value from the observation device  102  as an engine condition index. In step  210 , the learning unit  108  stores a combination of the plurality of engine command values output to the controller  103  and the plurality of engine condition indices input from the observation device  102  in the data server  105  as a data set for learning. 
     In step  211 , the learning unit  108  creates a learning model using the data set for learning. The learning unit  108  may create a learning model by learning parameters using the data set for learning with the parameters of the base learning models as initial values, instead of newly creating a learning model. 
     In step  212 , the learning unit  108  creates a label for the created learning model and stores the label in the data server  105 . The stored learning model is one of the base learning models in the subsequent process. 
     As described above, according to the embodiment, it is possible to compose the outputs of two learning models according to the characteristic ratio of the state indices of the two learning models even when there are only two learning models, thereby obtaining output values which cannot be output from each of the two learning models as a composed value. 
     Then, the searching is performed based on the obtained composed value, so that the data set for searching is stored and the command value with the maximum thermal efficiency is searched for in the data set for searching, whereby it is possible to obtain a command value with the maximum thermal efficiency which cannot be obtained from the composed value. It is also possible to create a new learning model using the command value with the maximum thermal efficiency. 
     Second Embodiment 
     In a second embodiment, an example will be described in which an engine command value not causing abnormal combustion is acquired for each operating condition in order to set the search range. In the embodiment, the difference from the first embodiment will be mainly described, and the same description as in the first embodiment will be omitted.  FIG. 3  is a diagram illustrating a configuration example of an engine system of this embodiment. 
     The PC  104  illustrated in  FIG. 3  includes a calibration unit  301  in addition to the learning model selecting unit  106  and the learning unit  108  illustrated in  FIG. 1 . After the engine  101  is started, the calibration unit  301  acquires an engine command value not causing abnormal combustion in the range of preset operating condition. Illustration of the processor  121 , the storage unit  122 , and the input/output unit  123  illustrated in  FIG. 1  is omitted. 
     The operating condition may be any condition as long as it affects the operation of the engine  101 . For example, as long as the engine operates by burning a plurality of types of fuel, the condition may be a mixing ratio of the plurality of types of fuel, but the condition is not limited thereto. In addition, a range, in which abnormal combustion does not occur, of the operating condition may be set in advance from the outside of the PC  104 . 
       FIGS. 4A and 4B  are diagrams illustrating an example of a process flowchart of the engine system according to the embodiment. The process of step  401  illustrated in  FIG. 4A  is the same as that of step  201  described with reference to  FIG. 2 . In step  402 , the learning model selecting unit  106  acquires a base learning model from the data server  105 . 
     That is, the learning model selecting unit  106  acquires the learning model having the shortest distance between the engine condition index output from the observation device  102  in step  401  and the engine condition indices of the labels of the plurality of learning models stored in the data server  105  as a base learning model. 
     Part of the plurality of engine condition indices acquired in step  401  may be used in step  402 . Not only the engine condition index, but also a target index such as a required torque or a combination of the engine condition index and the target index may be used in step  402 . 
     In step  403 , the calibration unit  301  inputs the engine condition index acquired in step  401  to the base learning model acquired in step  402  to obtain the output value. In step  404 , the calibration unit  301  stores the output value acquired in step  403  as an engine command value, and sets the deviation width of the engine command value and the deviation width of the target index. 
     Each of the deviation width of the engine command value and the deviation width of the target index may be set by the calibration unit  301  based on the value of the deviation width previously input to the PC  104 . 
     Then, the processing of step  430  is executed, and the description thereof will be given with reference to  FIG. 4B . In step  405  illustrated in  FIG. 4B , the calibration unit  301  outputs the stored engine command value to the controller  103 , and the controller  103  converts the output engine command value into a command signal and outputs the signal to the engine  101 . 
     In step  405 , the calibration unit  301  is further input with the state of the engine  101  with respect to the output engine command value from the observation device  102  as an engine condition index. In step  406 , the calibration unit  301  stores the combination of the engine condition index input from the observation device  102  and the command value output to the controller  103  as the calibration data set in the data server  105 . 
     In step  407 , the calibration unit  301  adds the deviation width of the target index to the target index to be updated, and stores the updated target index as a new target index. The process of step  408  is the same as that of step  401 . In step  409 , the calibration unit  301  adds the deviation width of the engine command value to the stored engine command value to be updated, and stores the updated command value as a new engine command value. 
     In step  410 , the calibration unit  301  determines whether the stored target index is within the operating condition range of the engine  101 . If it is determined that the stored target index is within the operating condition range, the process returns to step  405 , and if it is determined that the target index is not within the range, the process proceeds to step  411 . 
     A sensor for detecting abnormal combustion may be provided in the engine  101  and raw data of the sensor may be converted into an engine condition index relating to the presence or absence of abnormal combustion detection in the observation device  102 . The calibration unit  301  may be continuously input with an engine condition index relating to the presence or absence of abnormal combustion detection from the observation device  102  to determine a range where abnormal combustion is not detected. 
     In step  410 , instead of determining whether the stored target index is within the operating condition range of the engine  101 , the calibration unit  301  may determine whether the target index is within the range where abnormal combustion is not detected, or may determine whether the stored target index is within the operating condition range of the engine  101  and the range where abnormal combustion is not detected. 
     Step  411  is the same process as step  401 . In step  412 , the learning unit  108  acquires, from the calibration data stored in the data server  105 , a combination of the engine condition index and the engine command value closest to the engine condition index output from the observation device  102  in step  411 . 
     In step  413 , the learning unit  108  sets the search range in the same manner as in step  205  described with reference to  FIG. 2 , based on the engine command value acquired in step  412 . Returning to  FIG. 4A , processes of steps  414  to  420  are the same as those of steps  206  to  212  described with reference to  FIG. 2 . 
     As described above, according to the embodiment, it is also possible to avoid abnormal combustion when searching for a command value that maximizes thermal efficiency. 
     Third Embodiment 
     In a third embodiment, another example of acquiring the engine command value not causing abnormal combustion for each operating condition will be described. Since the configuration example of an engine system of this embodiment is the same as that of the second embodiment, the description thereof will be given with reference to  FIG. 3  and new illustration thereof will be omitted. 
       FIG. 5  is a diagram illustrating an example of a process flowchart of the engine system according to the embodiment. The processes of steps  501  and  502  are the same as those of steps  401  and  402  illustrated in  FIG. 4A . In step  503 , the calibration unit  301  inputs the combination of the engine condition index acquired in step  501  and the stored target index into the base learning model acquired in step  502 , and acquires an output value. 
     In step  504 , the learning unit  108  sets a search range in the same manner as in step  413 , based on the engine command value acquired in step  503 . The processes of steps  505  to  511  are the same as those of steps  414  to  420  illustrated in  FIG. 4A . Each of processes of steps  512  and  513  is the same as that of steps  407  and  410  illustrated in  FIG. 4B . The deviation width of the target index is set in advance before step  501 . 
     As described above, according to the embodiment as in the second embodiment, it is also possible to avoid abnormal combustion when searching for a command value that maximizes thermal efficiency. 
     Fourth Embodiment 
     In a fourth embodiment, based on the engine condition index output from the observation device  102 , an example will be described whether to select the setting of the search range based on the output value obtained by composing the outputs of two or more base learning models or the setting of the search range based on the output value of one base learning model. Since the configuration example of the engine system of the embodiment is the same as that of the first embodiment, the description thereof will be given with reference to  FIG. 1  and new illustration thereof will be omitted. 
       FIG. 6  is a diagram illustrating an example of a process flowchart of the engine system according to the embodiment. The process of step  601  is the same as that of step  201  described with reference to  FIG. 2 . In step  602 , the learning model selecting unit  106  acquires a group of base learning models from the data server  105 . 
     Then, the learning model selecting unit  106  determines whether the shortest distance between the engine condition index output from the observation device  102  in step  601  and the engine condition indices of the labels of the plurality of learning models stored in the data server  105  is smaller than a preset threshold value. 
     If it is determined that the shortest distance is smaller than the threshold value, the learning model selecting unit  106  acquires the learning model of the shortest distance as the base learning model and the process proceeds to step  603 . When it is determined that the shortest distance is not smaller than the threshold value, two or more learning models are acquired as the group of base learning models in ascending order of the distance, and the process proceeds to step  604 . 
     Part of the plurality of engine condition indices acquired in step  601  may be used in step  602 . Further, not only the engine condition index, but also a target index such as the required torque, or a combination of the engine condition index and the target index may be used in step  602 . 
     In step  603 , the learning unit  108  inputs the engine condition index acquired in step  601  to the base learning model acquired in step  602  to acquire the output value, and the process proceeds to step  606 . The processes of steps  604  to  613  are the same as those of steps  203  to  212  described with reference to  FIG. 2 . 
     As described above, according to the present embodiment, when a learning model matching with the combustion state of the engine is stored in the data server, composition processing becomes unnecessary, and the time required for searching is shortened.