Patent Publication Number: US-2022229427-A1

Title: Control apparatus and control system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-006569 filed on Jan. 19, 2021, the entire disclosure of which is incorporated by reference herein. 
     BACKGROUND 
     The present disclosure relates to a control apparatus for controlling a plant including a plurality of units and a control system including a plurality of plants. 
     For example, Toru Yamamoto, “Smart MBD (S-MBD) Technique based on Control Engineering Perspective—Proposal of New Development Platform—,” Journal C of the Institute of Electrical Engineers, Technical Meeting on Electronic/Information/System Control, Jun. 29, 2019, CT19099, pp. 25-26 discloses a development method in which a database-driven (DD) control system design method is combined with so-called model based development (MBD). Specifically, the document discloses, as an example of a design method for achieving desired performance of a system, a method of adjusting an adjustable parameter of a modeled system by a database mechanism. 
     SUMMARY 
     The inventors of the present application have considered that a design method based on a model as described in the above document is applied to general system control and a system including a plurality of units (e.g., an engine and a motor), such as a hybrid system or a steering system of an automobile, is operated as a control target (a plant). 
     It is assumed that the performance of such a plant changes due to aging and other causes as the plant is operated for a long period of time. For keeping the plant performance constant, the inventors of the present application have searched a mechanism for autonomously compensating for the changed performance by correcting the configuration of a model corresponding to the plant or an output value of the model as necessary. The inventors of the present application have focused on the fact that each plant includes the units, and have arrived at the present disclosure. 
     The present disclosure has been made in view of the above-described points, and an object thereof is to keep plant performance constant in a control apparatus for controlling a plant including a plurality of units. 
     Specifically, a first aspect of the present disclosure relates to a control apparatus for controlling a plant including a plurality of units. The control apparatus includes a model controller that generates a target value of a characteristic to be achieved by each unit based on a model set for each unit, a unit specifier that specifies a unit in which performance unique to the unit has changed among the units, and a target value corrector that corrects the target value for the unit that has been specified by the unit specifier. 
     According to the first aspect, the target value corrector performs correction of the target value for the unit specified by the unit specifier, i.e., the unit determined that the performance unique to the unit has changed, among the units. Accordingly, the performance of the plant is autonomously compensated, and can be kept constant. Moreover, by performing compensation for each unit instead of performing compensation for each plant, performance compensation can be achieved while a change in the control forms of other units is reduced as much as possible. 
     According to a second aspect of the present disclosure, the control apparatus may include a plurality of characteristic estimators that corresponds to the respective units and estimates the characteristic achieved by each unit, and a plant behavior estimator that estimates plant output of the plant based on the characteristic that has been estimated by each characteristic estimator. The target value corrector may correct the target value such that desired plant output is achieved. 
     Here, the term “plant output” refers to general plant output such as a vehicle speed in a case where an automobile is used as the plant. 
     According to the second aspect, the target value corrector corrects the target value of the characteristic to be achieved by the unit such that the desired plant output is achieved through correction of the target value. In this manner, by adjusting the plant output through compensation for each unit, adjustment of the plant output can be achieved while a change in the control forms of other units is reduced. 
     According to a third aspect of the present disclosure, the units may include a first unit contributing to an increase or decrease in predetermined plant output and a second unit contributing to an increase or decrease in the plant output common to the first unit. In a case where the unit specifier determines that the performance of one of the first unit or the second unit has changed, the model controller may increase or decrease the target value associated with the other one of the first unit or the second unit to compensate for the change. 
     According to the third aspect, in a case where the performance of the first unit has, for example, irreversibly greatly changed, the desired plant output can be achieved by an increase or decrease in the target value of the second unit. In this manner, other units autonomously recover a change in the performance, which is advantageous in keeping the plant performance constant. 
     According to a fourth aspect of the present disclosure, the target value corrector may correct the target value by correcting the model corresponding to the unit that has been specified by the unit specifier. 
     According to the fourth aspect, the model corresponding to the unit whose performance has changed is corrected, which is advantageous in compensating for a change in the performance of the unit and therefore keeping the plant performance constant. 
     According to a fifth aspect of the present disclosure, the control apparatus may further include a plurality of feedback sections that corresponds to the respective units. Each feedback section may generate, based on an output signal from the unit corresponding to the each feedback section, a feedback signal for correcting an output signal from the model controller to compensate for a difference between a characteristic actually achieved by the unit and the target value. Each feedback section may correct the output signal by adjusting an FB characteristic amount indicating any one of the feedback signal or an FB parameter indicating a coefficient contributing to an increase or decrease in the feedback signal based on the output signal from the unit. 
     According to the fifth aspect, feed forward control based on the model and feedback control are combined. This is advantageous in keeping the plant performance constant. 
     According to a sixth aspect of the present disclosure, each feedback section may input the FB characteristic amount to the unit specifier. Based on a change in the FB characteristic amount in each unit, the unit specifier may determine a change in the performance unique to the unit. The target value corrector may correct the model based on a change in the FB characteristic amount in each unit. 
     According to the sixth aspect, the model is corrected based on a change in the FB characteristic amount. This is advantageous in keeping the plant performance constant. 
     According to a seventh aspect of the present disclosure, the target value corrector may correct the target value through adjustment of the FB characteristic amount in a case where the moving average of the FB characteristic amount is less than a predetermined threshold, and may correct the target value through correction of the model in a case where the moving average of the FB characteristic amount is equal to or greater than the predetermined threshold. 
     According to the seventh aspect, for a change with a relatively-small change amount in a temporal performance change or an irreversible performance change, the target value is corrected by the feedback control. On the other hand, for a change with a relatively-great change amount in the irreversible performance change, the target value is corrected through correction of the model. In this manner, by selectively using these two correction methods, more flexible control is achieved, which is advantageous in keeping the plant performance constant. 
     According to an eighth aspect of the present disclosure, the control apparatus may further include a measurer that detects a measurement signal indicating operation environment of the plant. The unit specifier may determine a change in the performance unique to the unit based on the measurement signal of the measurer and the FB characteristic amount. 
     According to the eighth aspect, such control that a change in the performance of the unit is associated with the operation environment of the plant can be achieved. Accordingly, the performance of each unit can be more properly compensated. 
     According to a ninth aspect of the present disclosure, the control apparatus may further include a map generator that stores the operation environment of the plant, the FB characteristic amount, and an FF parameter as a parameter characterizing the model in association with each other. The target value corrector may collate the FF parameter corresponding to the FB characteristic amount based on the signal detected by the measurer and the FB characteristic amount. 
     According to the ninth aspect, such control that a change in the performance of the unit, the operation environment of the plant, and information associated with correction of the model are associated with each other can be achieved. Accordingly, the performance of each unit can be more properly compensated. 
     According to a tenth aspect of the present disclosure, the map generator may update, during drive of the plant, a relationship among the drive environment of the plant, the FB characteristic amount, and the FF parameter in real time. 
     According to the tenth aspect, such knowledge that a change in the performance of the unit, the operation environment of the plant, and the information associated with correction of the model are associated with each other can be obtained. This contributes to autonomous updating for the plant. 
     According to an eleventh aspect of the present disclosure, in a case where the unit specifier specifies a plurality of units, the timing of reflecting correction of the target value may be adjusted to the substantially identical timing among the units. 
     According to the eleventh aspect, the identical timing of correcting the target value is set to the extent possible, which is advantageous in reducing occurrence of unintended plant output and therefore keeping the plant performance constant. 
     According to a twelfth aspect of the present disclosure, the plant may be an automobile, and the units may include one or more of an engine and a motor that output torque for driving the automobile, a brake unit that puts a brake on the automobile, or a steering system that steers the automobile. 
     A thirteenth aspect of the present disclosure relates to a control system including a plurality of plants controlled by the respective control apparatuses. In the control system, each plant may include the units, and a specifying result of the unit specifier in any one of the plants may be shared among other plants. 
     According to the thirteenth aspect, information associated with a change in the performance of the unit can be shared among the plants. As described above, the knowledge obtained by the unit specifier is shared among the plants, and therefore, more autonomous control can be achieved. 
     According to a fourteenth aspect of the present disclosure, at least some of the control apparatuses may be mounted on an external server, and the plants may communicate with each other via the external server. 
     According to the fourteenth aspect, the information associated with a change in the performance of the unit can be exchanged among the plants via the external server. As described above, the knowledge obtained by the unit specifier is shared among the plants, and therefore, more autonomous control can be achieved. 
     As described above, according to the present disclosure, the plant performance can be kept constant in the control apparatus for controlling the plant including the units. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing, as an example, an entire configuration of a control system. 
         FIG. 2  is a diagram showing, as an example, the configuration of each plant in the control system. 
         FIG. 3  is a diagram showing, as an example, the configuration of a control apparatus of each plant. 
         FIG. 4  is a diagram for describing control of the plant by the control apparatus. 
         FIG. 5  is a diagram for describing estimation of a unit characteristic by a characteristic estimator. 
         FIG. 6  is a diagram for describing unit characteristic feedback control by a feedback section. 
         FIG. 7  is a flowchart showing, as an example, a main part of the control performed by the control apparatus. 
         FIG. 8  is a flowchart showing, as an example, a main part of the procedure of correcting a target value. 
         FIG. 9  is a graph for describing function distribution performed in control of the plant. 
         FIG. 10  is a graph for describing a change in unit performance over time. 
         FIG. 11  is a diagram for describing cooperation with an external server. 
         FIG. 12  is a diagram for describing cooperation among the plants in the control system. 
         FIG. 13  is a diagram for describing cooperation among the plant and factories. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present disclosure will be described. Note that the following description is merely illustrative. 
     That is, in the present specification, an automobile including an engine, a motor, and other components will be described as one example of a plant including a plurality of units, but the technique disclosed herein is not limited to application to the automobile. The present disclosure can be generally applied to a mechanical system including a plurality of units. 
     In particular, in the present specification, an engine, a motor, a brake, and a steering unit for driving an automobile will be described as examples of the units included in the plant. However, the units according to the present disclosure include general units associated with operation of the plant. Elements other than mechanical units, such as a driver of the automobile, can also be taken as units. 
     In addition, in the present specification, a PCM mounted on the automobile will be described as one example of a control apparatus of the plant, but the control apparatus according to the present disclosure is not limited to a module mounted on the plant. The control apparatus according to the present disclosure includes general equipment that can be connected to the plant in a wired or wireless manner, such as an external server. As in variations described later, part of the control apparatus may be implemented by the PCM, and the other part of the control apparatus may be implemented by the external server. 
     &lt;Entire Configuration&gt; 
       FIG. 1  is a diagram showing, as an example, an entire configuration of a control system S. Moreover,  FIG. 2  is a diagram showing, as an example, the configuration of each plant (each automobile C) in the control system S. As shown in  FIG. 1 , the control system S according to the present embodiment includes a plurality (n in the illustrated example) of automobiles C 1  to C n . Each of the automobiles C 1  to C n  indicates, as an example, the “plant” in the present embodiment. Unless otherwise limited to a particular automobile, an automobile will be hereinafter also simply referred to as an “automobile C.” 
     The automobiles C 1  to C n  are connected to each other via an external server Cs. One automobile C sends or receives an electrical signal to or from the other automobiles C via the external server Cs. Note that the external server Cs is not essential. It may be configured such that the automobiles C communicate with each other without the external server Cs. 
     As shown in  FIG. 2 , each automobile C includes a plurality (N in the illustrated example) of units  20   1  to  20   N . Specifically, each automobile C includes a first unit  20   1  having an engine, a second unit  20   2  having a motor, a third unit  20   3  having a brake unit, an N-th unit  20   N  having a steering system, and other units  20   4  to  20   N-1 . Each of the first unit  20   1  having the engine and the second unit  20   2  having the motor outputs torque for driving the automobile C. The third unit  203  having the brake unit puts a brake on the automobile C. The N-th unit  20 N having the steering system steers the automobile C. Each of the first unit  20   1  to the N-th unit  20   N  indicates, as an example, a “unit” in the present embodiment. Unless otherwise limited to a particular unit, a unit will be hereinafter also simply referred to as a “unit  20 .” These units  20  form a hardware system of the automobile C. 
     Each unit  20  is selected from elements capable of controlling the behavior of the automobile C. Note that the behavior of the automobile C described herein includes any index associated with the dynamic behavior of the automobile C. 
     Generally, “plant behavior” indicates an output value, i.e., a general plant output, controlled by a PCM  100 . As described later, in a case where model prediction control is performed by the PCM  100 , the behavior of the plant is equivalent to a plant output controlled to follow a predetermined set value trajectory. Hereinafter, the “behavior of the plant” and the “behavior of the automobile C” will be also referred to as “plant output.” 
     For example, the behavior of the automobile C in the present embodiment includes physical quantities associated with the unit according to the present disclosure among any physical quantities characterizing motion of the automobile C, such as the longitudinal speed, the lateral speed, the longitudinal acceleration, the lateral acceleration, and the yaw rate of the automobile C. Note that “longitudinal” in the present specification is equal to propulsion and reverse running directions of the automobile C. Similarly, “lateral” in the present specification is equal to a right-left turning direction of the automobile C. 
     More specifically, as described above, in a case where the engine, the motor, and the brake unit of the automobile C are taken as the units, the behavior of the automobile C may include physical quantities associated with propulsion of the automobile C, such as the longitudinal speed and the longitudinal acceleration. On the other hand, in a case where the units include the steering system, the behavior of the automobile C may include physical quantities associated with steering of the automobile C, such as the yaw rate. 
     Each unit  20  may have a plurality of sub-units. The sub-unit described herein is selected from elements capable of controlling the behavior of the corresponding unit  20 . In the example shown in  FIG. 2 , the first unit  20   1  has, as the sub-units, devices associated with operation of the engine. Specifically, the first unit  20   1  has, as the sub-units, a throttle valve  201   a  and an EGR valve  201   b . Although not shown, the second unit  20   2  may have, as devices associated with drive of the motor, an inverter, a DC/DC converter, and other components as the sub-units. According to the present disclosure, the sub-units of the unit  20  may be also indirectly controlled via control of the unit  20 . 
     As an element for controlling the automobile C as the plant, the PCM  100  as the control apparatus is mounted on each automobile C. The PCM  100  includes a CPU  100   a  that executes various types of arithmetic operation, a memory  100   b  that at least temporarily stores information necessary for the arithmetic operation performed by the CPU  100   a , and an input/output bus  100   c  that forms a path for data transmission/reception. The PCM  100  is connected to the above-described external server Cs such that an electrical signal is transmittable to or receivable from the external server Cs. In other words, the automobile C is connected to the external server Cs via the PCM  100  that controls the automobile C. 
     Sensors for detecting measurement signals associated with drive environment (operation environment) of the automobile C are wirelessly connected to the PCM  100  as the control apparatus. More specifically, a sensor not physically connected to each unit  20  is connected to the PCM  100  according to the present embodiment. That is, as the sensors according to the present embodiment, a sensor (a so-called external sensor) attachable to the outside of the unit  20 , such as a GPS sensor, may be selected in addition to a sensor, such as a crank angle sensor and a cylinder pressure sensor, physically directly attached to the unit  20  (e.g., an engine). 
     Such external sensors are configured to detect measurement signals associated with information (drive conditions) characterizing environment where the automobile C is located, such as an air pressure, a temperature, and an altitude, rather than information associated with the dynamic behavior of the automobile C, such as the speed and acceleration of the automobile C. 
     Specifically, the PCM  100  according to the present embodiment is connected to an external air temperature sensor SW 1  as an external sensor (a measurer) that detects a measurement signal indicating the operation environment of the plant and a vehicle speed sensor SW 2  as a non-external sensor. These sensors SW 1  to SW 2  and the PCM  100  together form the control system of the automobile C. 
     Moreover, a display apparatus  30  for displaying various types of information is connected to the PCM  100  in a wired or wireless manner. The display apparatus  30  may be configured using a liquid crystal display or an organic EL display, for example. 
       FIG. 3  is a diagram showing the configuration of the control apparatus (the PCM  100 ) of each plant (the automobile C). Moreover,  FIG. 4  is a diagram for describing control of the plant (the automobile C) by the control apparatus (the PCM  100 ).  FIG. 4  shows a relationship between a connection relationship among functional blocks shown as examples in  FIG. 3  and the dynamic behavior (dynamics) of the plant and the units. Hereinafter, the outline of each function implemented in the PCM  100  will be described with reference to  FIGS. 3 and 4 . 
     As shown in  FIG. 3 , the PCM  100  according to the present embodiment includes a first characteristic estimator  10   1  to an N-th characteristic estimator  10   N , a plant behavior estimator  11 , a plant behavior target generator  12 , a model controller  13 , and a first feedback section  14   1  to an N-th feedback section  14 N. These functional blocks are implemented by predetermined programs (e.g., pre-coded programs or programs input to function as an interpreter), and are read to the memory  100   b  as necessary. Of these functional blocks, the first characteristic estimator  10   1  to the N-th characteristic estimator  10   N  and the first feedback section  14   1  to the N-th feedback section  14   N  are both mounted so as to be the same number as that of the units  20 . The program corresponding to each functional block may be updated automatically or manually after the start of operation of the plant (the automobile C). 
     Hereinafter, the basic concept of processing implemented by each functional block will be described. 
     &lt;Basic Concept&gt; 
     Among the functional blocks described above, the first characteristic estimator  10   1  to the N-th characteristic estimator  10   N  determine performance (hereinafter referred to as “unit performance”) unique to each unit  20 , and set a model characterizing the characteristics (hereinafter referred to as a “unit characteristic”) of each of the first unit  20   1  to the N-th unit  20   N  based on the determined unit performance Hereinafter, the “first characteristic estimator  10   1 ” to the “N-th characteristic estimator  10   N ” may be collectively referred to as a “characteristic estimator  10 .” 
     The first characteristic estimator  10   1  to the N-th characteristic estimator  10   N  estimate the unit characteristic to be achieved by the unit  20  corresponding to each characteristic estimator based on the set model. The first characteristic estimator  10   1  to the N-th characteristic estimator  10   N  input estimation results to the plant behavior estimator  11 . Hereinafter, the estimated unit characteristic will be also referred to as an “estimated characteristic.” 
     Specifically, the model set by the characteristic estimator  10  is configured to output the unit characteristic according to the unit performance. The “unit characteristic” as described herein refers to a physical quantity contributing to an increase or decrease in the plant output. In other words, the unit characteristic of the present disclosure includes general characteristics contributing to an increase or decrease in the plant output. 
     For example, in a case where the engine, the motor, and the brake unit are used as the units  20  and the longitudinal acceleration or longitudinal speed of the automobile C is used as the plant output, e.g., engine torque, motor torque, and brake torque can be used as the unit characteristics corresponding to these settings. 
     Similarly, in a case where the steering unit and the brake unit are used as the units  20  and the yaw rate of the automobile C is used as the plant output, e.g., the position of a steering rack in the steering unit and the brake torque can be used as the unit characteristics corresponding to these settings. 
     The plant according to the present embodiment includes the units  20 . These units  20  may include the first unit  20   1  contributing to an increase or decrease in predetermined plant output, and the second unit  20   2  contributing to an increase or decrease in plant output common to the first unit  20   1 . In the example described above, in a case where the plant output is set to the longitudinal acceleration or longitudinal speed of the automobile C, each of the first and second units  20   1 ,  20   2  corresponds to an optional combination of the engine, the motor, and the brake unit. Similarly, in a case where the plant output is set to the yaw rate of the automobile C, the first and second units  20   1 ,  20   2  respectively correspond to the steering unit and the brake unit. 
     The unit performance determined by the characteristic estimator  10  includes performance contributing to an increase or decrease in the unit characteristic such as the engine torque and therefore a general coefficient obtained by parameterizing such performance. 
     For example, in a case where the engine torque is used as the unit characteristic, e.g., a tire radius, a gear ratio, a vehicle body weight, an air resistance, a gradient resistance, a brake pad resistance (the friction resistance of a brake pad), a hub resistance (the friction resistance of a hub), and the inertia moment of a tire can be used as the unit performance corresponding to such a unit characteristic. The characteristic estimator  10  sets such a model that the acceleration of the engine is taken as input and the engine torque is taken as output, using such unit performance as a parameter. 
     The characteristic estimator  10  determines a change in the unit performance as described above. The characteristic estimator  10  can correct the model (hereinafter also referred to as a “unit model”) based on a determination result of a change in the unit performance to compensate for such a change. 
     The characteristic estimator  10  includes, as functional blocks for implementing determination of the unit performance and correction of the model, a performance change determinator (a unit specifier)  10   a  and an FF updater (a target value corrector)  10   b . For example, the FF updater  10   b  specifies the unit  20  whose unit performance has changed among the units  20  based on a later-described FB characteristic amount input from the corresponding feedback section  14 . For example, the FF updater  10   b  corrects the unit model corresponding to the unit  20  specified by the performance change determinator  10   a , thereby correcting a later-described target value (a target characteristic) output from the model controller  13 . Details of these functional blocks will be described later. 
     The plant behavior estimator  11  estimates behavior achieved by the plant (the automobile C) based on the estimated characteristics output from the first characteristic estimator  10   1  to the N-th characteristic estimator  10   N . The plant behavior estimator  11  inputs such an estimation result to the model controller  13 . 
     As described above, the plant output closely relates to the unit characteristic of each unit  20 . The plant output can be modeled as a function using the unit characteristic of each unit  20  as input. The function (hereinafter also referred to as a “plant model”) obtained by modeling of the plant output is, as necessary, read from, e.g., the memory  100   b , and used, by the plant behavior estimator  11  and the model controller  13 . 
     For example, in a case where the engine torque and the motor torque are used as the unit characteristics, the longitudinal acceleration or longitudinal speed of the automobile C can be used as the plant output corresponding to the engine torque and the motor torque, as described above. In this case, the plant output can be described by a model in which a coupling structure from a power train including the engine and the motor to the tire (particularly a driving wheel) is formulated and an additional value of the engine torque and the motor torque is used as an input. 
     That is, the characteristic estimator  10  and the plant behavior estimator  11  can be regarded as a modeled relationship between the unit characteristic and the plant output. By tracing back this relationship, the unit characteristic (a target value of the characteristic to be achieved by each unit) corresponding to desired plant output and therefore the model setting for achieving the unit characteristic can be autonomously corrected. 
     The plant behavior target generator  12  generates a target value of the behavior to be achieved by the automobile C as the plant. As described later, in a case where the model controller  13  performs the model prediction control, the target value is equivalent to the so-called set value trajectory. In a case where the longitudinal acceleration of the automobile C is used as the plant output, the plant behavior target generator  12  generates a target value of the longitudinal acceleration (specifically, a longitudinal acceleration to be achieved in the future). Such generation of the target value can be performed based on a measurement signal associated with an interface for driving the automobile C, such as the accelerator position of the automobile C. For example, in a case where the yaw rate of the automobile C is used as the plant output, generation of a target value associated therewith can be performed based on the rotation angle of a steering wheel. 
     The model controller  13  generates a target value of the characteristic (the unit characteristic) to be achieved by each unit  20  based on the model (the unit model) set for each unit  20 . Specifically, the model controller  13  calculates a command value of each unit  20  based on the plant output (estimated behavior) estimated by the plant behavior estimator  11 , the unit characteristic (the estimated characteristic) estimated by the characteristic estimator  10 , and the model corrected by the characteristic estimator  10 . Note that in a case where the units  20  include a unit  20  having a sub-unit, a command value corresponding to such a sub-unit may be calculated. The model controller  13  calculates at least the same number of command values as that of the units  20 . The command values calculated by the model controller  13  are input to any one of the first feedback section  141  to the N-th feedback section  14 N corresponding to the respective units  20 . 
     The command value calculated by the model controller  13  corresponds to the target value of the unit characteristic of each unit  20 . That is, in a case where the longitudinal acceleration of the automobile C is used as the estimated behavior, the model controller  13  calculates, e.g., a target value of the engine torque, and a target value of the motor torque. Such calculation is implemented in such a manner that the unit characteristic corresponding to the plant output to be achieved is calculated back based on the plant model and the unit model. 
     Particularly, the model controller  13  of the present embodiment can execute the model prediction control. In the case of such a configuration, input to the model controller  13  is discretized into a multi-level system. Specifically, the model controller  13  takes, as input, the unit characteristic, plant behavior, and model estimated or corrected at timing one step ahead of the current time, and the unit characteristic, plant behavior, and model estimated or corrected at timing two steps ahead of the current time, thereby correcting the target value of the unit characteristic of each unit  20  by using the target value generated by the plant behavior target generator  12  as the set value trajectory. 
     Here, as described above, in a case where the units  20  include the first unit  20   1  contributing to an increase or decrease in the predetermined plant output and the second unit  20   2  contributing to an increase or decrease in the plant output common to the first unit  20   1 , the plant output as the plant behavior increases or decreases according to the additional value of the unit characteristics. For example, in a case where the engine torque and the motor torque are used as the unit characteristics, the plant output corresponding thereto can be described by a model taking, as input, the additional value of the engine torque and the motor torque, as described above. In this case, the model controller  13  can output a target value of the additional value of the engine torque and the motor torque. 
     Thus, for arithmetic operation for obtaining the target value of the engine torque and the target value of the motor torque, it is necessary to properly distribute the target value of the additional value to each unit  20 . Thus, the model controller  13  of the present embodiment changes distribution of the plant output according to the unit performance determined by each characteristic estimator  10 . Specifically, in a case where the characteristic estimator  10  determines that the performance of one of the first unit  20   1  or the second unit  20   2  has changed, the model controller  13  increases or decreases the target value of the other one of the first unit  20   1  or the second unit  20   2  to compensate for such a change. For example, in a case where the target value of the unit characteristic is corrected as a result of a change in the performance of the engine as the first unit  20   1  over time, it is assumed that an engine torque lower than a desired engine torque is output, and the target value of the motor torque of the motor as the second unit  20   2  is set high. 
       FIG. 9  is a graph for describing function distribution performed in control of the plant, particularly the automobile C. As shown in  FIG. 9 , the PCM  100  reads a map defined for distribution of the plant output. In  FIG. 9 , the sum of the engine torque (ENG TORQUE) and the motor torque (MG TORQUE) is constant on a line Lt. The line Lt shifts according to a drive state of the automobile C. In an example shown in  FIG. 9 , the line Lt shifts upward in a case where the automobile C accelerates or travels at a high speed, as indicated by a one-dot-chain line. Here, it is assumed that the motor torque and the engine torque are distributed as shown in a plot P 2  at an initial point of time. Here, as described above, in a case where aging of the engine is determined, the model controller  13  changes distribution of torque from the plot P 2  to a plot P 1 . Accordingly, the engine torque is set low while the motor torque is set high. For example, a map defined for current distribution may be stored with the map being associated with the drive environment (the drive conditions) of the automobile C. In this case, every time the automobile C is started, the PCM  100  can read a map suitable for current drive environment to use the map for distribution of the plant output. 
     The first feedback section  14   1  to the N-th feedback section  14   N  are provided so as to correspond to the respective units  20 , and correct the target value of the unit characteristic calculated for each unit  20 . Hereinafter, the “first feedback section  14   1 ” to the “N-th feedback section  14   N ” may be collectively referred to as a “feedback section  14 .” 
     Specifically, the first feedback section  14   1  to the N-th feedback section  14   N  each correct the output signal of the model controller  13  based on an output signal from the unit  20  corresponding to each feedback section  14  to reduce a difference between the unit characteristic (hereinafter also referred to as an “actual characteristic”) actually achieved by the unit  20  and the target value (hereinafter also referred to as a “target characteristic”) input from the model controller  13 . For performing such correction, the first feedback section  141  to the N-th feedback section  14   N  each generate a feedback signal (equivalent to a FB characteristic amount in  FIG. 5 ) corresponding to each unit  20 . 
     As the feedback signal, a signal based on a difference or a ratio between the actual characteristic and the target characteristic can be used. For example, in a case where PID control based on the difference between the actual characteristic and the target characteristic is performed, the feedback signal is a signal obtained by addition of the product (the proportional term) of the difference and a proportional gain, the product (the integral term) of an integral value of the difference and an integral gain, and the product (the differential term) of a differential value of the difference and a differential gain. In a case where the difference between the actual characteristic and the target characteristic is used, the feedback section  14  adds the feedback signal calculated in the above-described manner and an electrical signal corresponding to the target characteristic, thereby correcting the target characteristic. The feedback section  14  is provided for each unit  20 . Thus, such correction is executed in units of the unit  20 . 
     Moreover, the feedback section  14  changes, based on the output signal from the corresponding unit  20 , the FB characteristic amount indicating any one of the feedback signal or an FB parameter indicating a coefficient contributing to an increase or decrease in the feedback signal. 
     For example, in a case where PID-type feedback control is performed, the FB parameter is equivalent to the proportional gain, the integral gain, and the differential gain. The feedback section  14  adjusts the FB characteristic amount, thereby correcting the target characteristic and compensating for a change in the unit performance. For example, in a case where the actual characteristic of the corresponding unit  20  changes relatively greatly, the FB characteristic amount is greatly adjusted as compared to a case where the actual characteristic changes relatively slightly. Accordingly, feedback control that follows a change in the unit performance can be implemented. 
     More specifically, the feedback section  14  of the present embodiment adjusts the FB characteristic amount by data driven control. In this case, the unit characteristic achieved by the corresponding unit  20  is directly input to each feedback section  14  as in adaptive feedback control, or the unit characteristic is indirectly input to each feedback section  14  via a database as in so-called database type data driven control. Both types of control can be implemented by the feedback section  14 . 
     Moreover, each feedback section  14  inputs the FB characteristic amount to the corresponding performance change determinator  10   a . The performance change determinator  10   a  determines a change in the unit performance based on a change in the FB characteristic amount in each unit  20 . For example, in a case where the FB feature greatly changes, it can be determined that there is a high possibility that the unit performance changes, as compared to a case where the FB characteristic amount slightly changes. Moreover, in a case where a change in the FB characteristic amount is not temporary, but is continuously made, it can be determined that there is a high possibility that the unit performance irreversibly changes. Thus, the performance change determinator  10   a  determines whether or not the moving average of the FB characteristic amounts exceeds a predetermined threshold, and counts the number of times that the moving average exceeds the predetermined threshold. The performance change determinator  10   a  determines whether or not the number of times counted in the above-described manner exceeds a predetermined number of times within a predetermined period, and if such determination is NO (or if the moving average is less than the predetermined threshold), adjusts the FB characteristic amount by, e.g., the data driven control, and corrects the target characteristic to compensate for a change in the unit performance. 
     On the other hand, if such determination is YES (or if the moving average is equal to or greater than the predetermined threshold), the performance change determinator  10   a  corrects, as described above, the unit model via the FF updater  10   b , thereby correcting the target characteristic and therefore compensating for a change in the unit performance Here, the FF updater  10   b  updates the model by increasing or decreasing a parameter characterizing the unit model. Note that the FF updater  10   b  inputs, to the model controller  13 , signals indicating that the model has been updated and indicating the updated parameter. The model controller  13  can change distribution of the plant output based on the signals input as described above. 
     The target characteristic corrected by the feedback section  14  is input to the corresponding unit  20  as the command value corresponding to the corresponding unit  20 . 
     In the case of the present embodiment, the command value corrected by the first feedback section (the first FB section)  14   1  is input to the first unit (the engine)  20   1 . The first unit  20   1  outputs the engine torque as the actual characteristic of the engine based on dynamics D 1  corresponding to the unit performance at the time of inputting the command value. The signal indicating the engine torque is input to the first feedback section (the first FB section)  14   1 , and the first feedback section  14   1  executes the feedback control based on the FB characteristic amount, correction of the unit model of the engine, for example. 
     Similarly, the command value corrected by the second feedback section (the second FB section)  14   2  is input to the second unit (the motor)  20   2 . The second unit  20   2  outputs, as the actual characteristic of the motor, the actually-achieved motor torque based on dynamics D 2  corresponding to the unit performance at the time of inputting the command value. The signal indicating the motor torque is input to the second feedback section (the second FB section)  14   2 , and the second feedback section  14   2  executes the feedback control based on the FB characteristic amount, correction of the unit model of the motor, for example. 
     The automobile C as the plant outputs, for example, the longitudinal speed, the longitudinal acceleration as the plant output based on the engine torque output by the engine as the first unit  20   1 , the motor torque output by the motor as the second unit, and dynamics D p  corresponding to the performance of the first and second units  20   1 ,  20   2  at the time of inputting the engine torque and the motor torque. 
     That is, the unit characteristic estimated by the first characteristic estimator  10   1 , the unit characteristic estimated by the second characteristic estimator  10   2 , and the plant output (the estimated behavior) estimated by the plant behavior estimator  11  respectively correspond to the unit characteristic achieved by the first unit  20   1 , the unit characteristic achieved by the second unit  20   2 , and the plant output (actual behavior) achieved by the automobile. 
     In a case where the performance unique to each unit  20  is kept constant and the model prediction control by the model controller  13  is performed with favorable accuracy, each unit characteristic and the plant output substantially match each other. The unit model described above is equivalent to the model of the dynamics D 1 , D 2  of the corresponding unit  20 , and the plant model is equivalent to the model of the dynamics D p  of the entire plant. Thus, in a case where a performance change such as aging occurs in any of the units  20 , it is possible to compensate for the performance change only by correction of the model corresponding to the unit  20  in which the performance change has occurred without the need for changing the plant model and therefore the unit models of all of the units  20 . 
     Hereinafter, each functional block will be sequentially described in more detail. 
     &lt;Detailed Configuration&gt; 
     —Characteristic Estimator  10 — 
       FIG. 5  is a diagram for describing estimation of the unit characteristic by the characteristic estimator  10 . As shown in  FIG. 5 , the characteristic estimator  10  includes a unit characteristic estimator  10   c , a map generator  10   d , and a model generator  10   e  in addition to the performance change determinator  10   a  and the FF updater  10   b  described above. In an illustrated example, only the first characteristic estimator  10   1  is shown, but the same also applies to the configuration of the second characteristic estimator  102 . 
     As described above, the performance change determinator  10   a  determines a change in the corresponding unit performance based on the multileveled command value and the FB characteristic amount. Here, the measurement signal of the external air temperature sensor SW 1  as the external sensor is also input to the performance change determinator  10   a . Thus, e.g., the air resistance may change according to an air density and therefore an external air temperature. As described above, although the air resistance may influence optimization of the unit performance and therefore the unit model, such influence is considered to be temporal influence. For this reason, it is not proper to consider influence caused due to the drive environment (external environment), which includes the air resistance, of the automobile C as a change in the unit performance over time. 
     Thus, the performance change determinator  10   a  determines a change in the unit performance based on the drive environment of the automobile C (the operation environment of the plant) detected by the external sensor such as the external air temperature sensor SW 1  and the FB characteristic amount. For example, the PCM  100  or a secondary storage apparatus connected to the PCM  100  stores, for example, a database, a map, and a model in which the FB characteristic amount and the drive environment are associated with an index for determining a change in the unit performance. The performance change determinator  10   a  inputs the FB characteristic amount input from the feedback section  14  and the current drive environment to, e.g., the database, thereby determining whether the input FB characteristic amount indicates a temporal change in the unit performance or a continuous change (an irreversible change) in the unit performance. 
     Note that as information associated with the drive environment, an altitude, an atmospheric pressure, and other factors at a point where the automobile C is traveling can be used. Such information can be measured by a GPS sensor as an external sensor, for example. The PCM  100  can determine a change in the unit performance using the altitude, the air pressure, and other factors instead of or in addition to the external air temperature. Instead of or in addition to the measurement signal from the external sensor, a travel distance (an operation period of a plant in the case of a more general plant) of the automobile C may be recorded, and a change in the unit performance may be determined with reference to the recorded contents. 
     As in description of the schematic configuration of the characteristic estimator  10 , the unit characteristic estimator  10   c  estimates which unit performance has changed among a plurality of unit performances set for each unit  20  and to what extent the unit performance has changed. Such estimation can be performed based on the amount of change in the FB characteristic amount (particularly, a difference between the moving average of the FB characteristic amount and the predetermined threshold) and the drive environment or driving state of the automobile C. 
     For example, in the case of the engine as the first unit  20   1 , the unit characteristic estimator  10   c  can estimate a change in the performance of the engine by associating a change in the opening degree of the throttle valve  201   a  as the sub-unit forming the engine with the amount of change in the FB characteristic amount directly or indirectly contributing to the engine torque. More specifically, the unit characteristic estimator  10   c  can estimate a change in the performance in detail by associating a control target of the sub-unit forming each unit  20  with a change in the FB characteristic amount over time. Note that the “FB characteristic amount” in this example refers to an FB characteristic amount contributing to the opening degree of the throttle valve  201   a  (more specifically, the FB characteristic amount of torque acting on the throttle valve  201   a ). Since an intake air amount of the engine and therefore the engine torque are determined according to the opening degree of the throttle valve  201   a , the FB characteristic amount can be taken as the FB characteristic amount indirectly contributing to the engine torque. 
     For example, if the FB characteristic amount increases in a single uniform way regardless of the opening degree of the throttle valve  201   a , it can be determined that reactive force acting on a valve body of the throttle valve  201   a  has changed. In this case, it can be determined that a change has occurred in the performance of a return spring forming the throttle valve  201   a  (e.g., settling of the return spring has occurred). Similarly, for example, when the opening speed of the throttle valve  201   a  is constant, the FB characteristic amount is also constant. On the other hand, when the opening speed increases or decreases, in a situation where the FB characteristic amount increases or decreases, it can be determined that a change has occurred in the inertia moment of the throttle valve  201   a . In this case, it can be determined that a foreign matter has adhered to the valve body or that the shape of the valve body has changed. It is also possible to determine to what extent each change has progressed by determining a combination of a change in the reactive force and a change in the inertia moment. 
     Note that the determination result obtained by the unit characteristic estimator  10   c  can be displayed on the display apparatus  30  of the automobile C. Accordingly, the driver can grasp the current performance of the automobile C. Further, as described later, the determination result obtained by the unit characteristic estimator  10   c  can be, as knowledge obtained by the automobile C, shared with other automobiles C via the external server Cs or be transmitted to a factory, for example. 
     The map generator  10   d  stores a map in which the drive environment of the automobile C (the operation environment of the plant), the FB characteristic amount, and an FF parameter as a parameter characterizing the model are associated with each other. The FF parameter refers to parameters, such as the tire radius and the gear ratio, used in formulation of the unit model. Instead of the map, a simpler database may be used. The map generator  10   d  can update, during drive of the automobile C, a relationship among the drive environment of the automobile C, the FB characteristic amount, and the FF parameter in real time. 
     For example, as the unit performance changes, the FF parameter is updated in real time as described above. Accordingly, the unit model of the engine is corrected. Note that when the unit model of the engine is corrected, the PCM  100  can also change distribution of the plant output based on the unit characteristic corresponding to the unit model and the plant output, as described above. For example, a case is assumed, in which the maximum value of the engine torque as the unit characteristic has decreased as a result of clogging of an injector of the engine. In such a case, the desired plant output might not be achieved depending on the setting of the target torque. Such a possibility is particularly noticeable in a case where maximization of the plant output or maximization of the energy efficiency of the plant is required. In this case, as described with reference to  FIG. 9 , the PCM  100  achieves the desired plant output by compensating for a change in the maximum value of the engine torque with the motor torque. On the other hand, for example, in a case where the target torque is not so great and maximization of the energy efficiency is not required, compensation with the motor torque is not necessary, and therefore, a distribution change as described above is not necessary. As described above, the PCM  100  is configured to change distribution of the plant output according to the target setting of the plant output. 
     With the map generator  10   d , various factors such as a change in the unit performance in the unit  20  different from the corresponding unit  20  can be reflected in the model control. A change in the performance of the corresponding unit  20  “alone” is reflected in the model control so that the plant performance can be more reliably exhibited according to a developer&#39;s intention. The function of the model-based control can be more reliably implemented in such a manner that the knowledge of each unit characteristic associated with degradation of each unit  20  and variations in the performance of each unit  20  is accumulated. 
     The model generator  10   e  generates a model corresponding to the map by regression performed for the map generated by the map generator  10   d . The model generated by the model generator  10   e  is a model in which the drive environment of the automobile C (the operation environment of the plant), the FB characteristic amount, and the FF parameter corresponding to each unit performance are associated with each other. Note that both of the map generator  10   d  and the model generator  10   e  are not essential. 
     The FF updater  10   b  reflects the FF parameter newly obtained by collation of the map, the model, and other factors in the unit model, thereby updating the unit model. In a case where the FF parameter characterizing the unit model also influences the form of the plant model, the FF updater  10   b  outputs the updated FF parameter to the plant behavior estimator  11  and the model controller  13 . With such output, the unit model and the plant model are updated. 
     —Feedback Section  14 — 
       FIG. 6  is a diagram for describing the unit characteristic feedback control by the feedback section  14 . As shown in  FIG. 6 , the first feedback section  14   1  as the feedback section  14  includes an FB updater  14   a , an FB command value generator  14   b , a target characteristic corrector  14   c , and a timing adjuster  14   d . As shown in the figure, the second feedback section  142  has a configuration similar to that of the first feedback section  141 . Hereinafter, only the configuration of the first feedback section  14   1  will be described, except for a configuration associated with cooperation between the feedback sections  14 . 
     The FB updater  14   a  updates the FB parameter for increasing or decreasing the FB characteristic amount based on the difference or ratio between the target characteristic output from the model controller  13  and the actual characteristic in the first unit  20   1 . As described above, for example, in a case where the PID-type feedback control is performed, the FB parameter is equivalent to the proportional gain, the integral gain, and the differential gain. As a method of updating the FB parameter, a general method included in the data driven control can be used. For example, the FB parameter may be updated by the general adaptive control, or may be updated with reference to a database, a map, a model, and other factors. 
     Although not shown, the FB updater  14   a  of the present embodiment can update, in real time, the map and the model associated with each other such that one or more of the drive environment of the automobile C, the target characteristic, and the actual characteristic are taken as input and the FB parameter is taken as output, as in the map generator  10   d  and the model generator  10   e  in the characteristic estimator  10 . The FB updater  14   a  can also derive, by machine learning, such a relational expression that one or more of the drive environment of the automobile C, the target characteristic, and the actual characteristic are taken as input and the FB parameter is taken as output, regardless of the form of the model set in advance. In this case, the FB updater  14   a  also functions as a regression learner. 
     The FB updater  14   a  inputs the updated FB parameter to the FB command value generator  14   b . Further, in a case where the FB parameter is used as the FB characteristic amount, the FB parameter updated by the FB updater  14   a  is branched off from between the FB updater  14   a  and the FB command value generator  14   b , and is input to the characteristic estimator (specifically, the first characteristic estimator  10   1 )  10  associated with the unit  20  common to the feedback section  14 . Instead of directly inputting the FB parameter, the amount of change in the FB parameter may be input to the characteristic estimator  10 . 
     The FB command value generator  14   b  generates a feedback signal indicating a correction value (an FB value) of the target characteristic based on the FB parameter updated by the FB updater  14   a  and the difference between the target characteristic and the actual characteristic. 
     As already described above, in a case where the PID-type feedback control is performed, the FB value is the sum of the proportional term, the integral term, and the differential term with the difference as an argument. However, the feedback section  14  of the present embodiment is not limited to such a value. For example, the signal indicating the FB value can be also generated based on the ratio between the target characteristic and the actual characteristic. 
     In a case where the FB value is used as the FB characteristic amount, the FB value calculated by the FB command value generator  14   b  is branched off from between the FB command value generator  14   b  and the target characteristic corrector  14   c , and is input to the characteristic estimator (specifically, the first characteristic estimator  10   i )  10  associated with the unit  20  common to the feedback section  14 . 
     The target characteristic corrector  14   c  corrects the target characteristic based on the target characteristic (the FF value) output from the model controller  13  and the correction value (the FB value) generated by the FB command value generator  14   b.    
     Here, in a case where the feedback section  14  performs the PID control based on the difference between the target characteristic and the actual characteristic, the target characteristic corrector  14   c  functions as an adder that outputs an electrical signal corresponding to the sum of the FF value and the FB value. On the other hand, in a case where the feedback control is performed based on the ratio between the target characteristic and the actual characteristic, the target characteristic corrector  14   c  functions as a multiplier that outputs an electrical signal corresponding to the product of the FF value and the FB value. In an illustrated example, only the former configuration is shown, but the present disclosure also includes the latter configuration. 
     In a case where there are one or more units specified by the unit specifier, i.e., one or more units  20  whose performance is determined to have changed by the performance change determinator  10   a  among the units  20 , the timing adjuster  14   d  sets the timing of reflecting correction of the target characteristic to the substantially same timing among the units  20 . More specifically, the timing adjuster  14   d  sets the timing as described above for the unit  20  contributing to an increase or decrease in the plant output that is common among the units  20 . The combination of the units  20  as described above includes the combination of the steering unit and the brake unit in addition to the combination of the motor, the engine, and the brake unit as shown in the figure. 
     In a case where the unit specifier specifies a plurality of units, the target value corrector sets the timing of reflecting correction of the target value to the substantially same timing among the units. 
     &lt;Example of Control&gt; 
     Hereinafter, a main part of the control implemented by the control apparatus configured as described above will be described. In an example described below, the control apparatus is equivalent to the PCM  100  mounted on the automobile C as the plant, and the units  20  controlled by the PCM  100  are equivalent to the first unit  20   1  including the engine and the second unit  20   2  including the motor, as described above. 
       FIG. 7  is a flowchart showing, as an example, the main part of the control performed by the control apparatus (the PCM  100 ). Moreover,  FIG. 8  is a flowchart showing, as an example, a main part of the procedure of correcting the target characteristic. The flows shown in  FIGS. 7 and 8  are repeatedly executed while the automobile C is being driven. 
     First, as shown in Step S 1  of  FIG. 7 , the characteristic estimator  10  estimates the unit characteristic. The unit characteristic are estimated for each unit  20 . Subsequently, in Step S 2 , the plant behavior estimator  11  estimates the plant behavior (the plant output) based on the estimated unit characteristic. Note that in a case where the model controller  13  performs the model prediction control, estimation of the unit characteristic and estimation of the plant behavior are performed for each multileveled time point. 
     Then, in Step S 3 , the model controller  13  generates, for example, the target value (the target characteristic) by the model prediction control based on the estimated unit characteristic and plant behavior. The target value is generated for each unit  20 . 
     In Step S 4 , before, after, or in parallel with generation of the target value in Step S 3 , the performance change determinator  10   a  in the characteristic estimator  10  specifies the unit  20  whose performance has changed among the units  20  forming the automobile C as the plant based on the actual unit characteristic (the actual characteristic). Note that the order of the steps in  FIG. 7  is merely an example. For example, Step S 4  may be executed in advance of Step S 1 . 
     In Step S 5 , the FF updater  10   b  in the characteristic estimator  10  corrects the model associated with the unit specified in Step S 4 . The target characteristic is corrected through correction of the model by the FF updater  10   b.    
     In Step S 6 , function distribution among the units  20  is changed as described with reference to  FIG. 9 . Specifically, the model controller  13  adjusts the ratio between the target characteristic of the engine as the first unit  20   1  and the target characteristic of the motor as the second unit  20   2  such that the behavior (the plant output) to be achieved by the automobile C is constant. Such processing can be performed based on the parameter characterizing the drive state of the automobile C, such as the measurement signal of the vehicle speed sensor SW 2 . 
     In Step S 7 , the corrected target characteristic is input to the unit  20 . Each unit  20  achieves such a characteristic that the correction result of the target characteristic is reflected in the unit characteristic estimated in Step S 1 , and in response to such a corrected characteristic, the automobile C achieves the plant behavior (the actual behavior) similar to the plant behavior estimated in Step S 2 . 
     Here, the specific procedure of adjusting the target characteristic is as shown in  FIG. 8 . First, as shown in Step S 11 , the characteristic estimator  10  sets a normative characteristic of the unit  20  based on, e.g., the current drive environment. Subsequently, as shown in Step S 12 , the characteristic estimator  10  reads the FB characteristic amount calculated by the feedback section  14 . 
     Then, in subsequent Step S 13 , the characteristic estimator  10  determines, based on the characteristic of the unit  20  estimated based on the current FB characteristic amount, whether or not the characteristic estimated by the characteristic estimator  10  is the normative characteristic. If such determination is YES, the characteristic estimator  10  determines that the current system behavior is proper, and the model controller  13  generates the FF value and the processing returns. In this case, the PCM  100  executes the model prediction control in a state in which the FB parameter is fixed and the model corresponding to each unit  20  is not changed. As shown in ( 1 ) of  FIG. 10 , this state corresponds to a state in which the unit  20  does not change over time and the unit performance thereof is maintained constant or a state in which a change has occurred over time and is compensated for by updating of the FF parameter or the FB parameter (a state in which the normative characteristic reflecting the updated FF parameter or FB parameter is achieved). 
     On the other hand, is the determination in Step S 13  is NO, the characteristic estimator  10  determines, in Step S 14 , whether or not a response characteristic of the unit  20  can be improved (whether or not improvement can be made by FB characteristic amount adjustment?). If such determination is YES, the feedback section  14  corresponding to the unit  20  updates the FB parameter as shown in Step S 15 , and the model controller  13  generates the FF value and the processing returns. In this case, the PCM  100  executes the model prediction control in a state in which the FB parameter is fixed and the model corresponding to each unit  20  is not changed. As indicated by a solid line in ( 2 ) of  FIG. 10 , this state corresponds to a state in which the unit performance has been degraded due to a change in the unit  20  over time, but influence of such degradation is compensated for by updating of the FB parameter. Note that a chain line in  FIG. 10  corresponds to a performance curve in a case where neither the FB parameter nor the FF parameter is updated. 
     If the determination in Step S 14  is NO, the characteristic estimator  10  determines that the unit performance of the unit  20  has irreversibly greatly changed. In this case, the characteristic estimator  10  updates the FF parameter, the model controller  13  generates the FF value, and the processing returns. In this case, as shown in Step S 16 , the PCM  100  executes the model prediction control in a state in which the FB parameter has been changed and the FF parameter characterizing the model corresponding to each unit  20  has been changed. As shown in ( 3 ) of  FIG. 10 , this state corresponds to a state in which the unit performance has been greatly degraded due to a change in the unit  20  over time, but influence of such degradation is compensated for by updating of the FB parameter and a model change (updating of the FF parameter). 
     As described above, according to the present embodiment, the FF updater  10   b  performs correction of the characteristic target for the unit  20  specified by the performance change determinator  10   a , i.e., the unit  20  determined that the performance unique to the unit has changed, among the units  20 . Accordingly, the performance of the automobile C is autonomously compensated and can be kept constant. Moreover, by performing compensation for each unit  20  instead of performing compensation for each automobile C, performance compensation can be achieved while a change in the control forms of other units  20  is reduced as much as possible. 
     In addition, the FF updater  10   b  achieves the desired plant output by correcting the target characteristic through correction of the model corresponding to the specified unit  20 . In this manner, by adjusting the plant output through compensation for each unit  20 , adjustment of the plant output can be achieved while a change in the control forms of other units  20  is reduced. 
     Further, as described with reference to  FIG. 9 , in a case where the performance of the first unit  20   1  has, for example, irreversibly greatly changed, the desired plant output can be achieved by an increase or decrease in the target value of the second unit  20   2 . In this manner, other units  20  autonomously recover a change in the performance, which is advantageous in keeping the performance of the automobile C constant. 
     For a change with a relatively-small change amount in a temporal performance change or an irreversible performance change, the characteristic target is corrected by the feedback control. On the other hand, for a change with a relatively-great change amount in the irreversible performance change, the characteristic target is corrected through correction of the model. In this manner, by selectively using these two correction methods, more flexible control is achieved, which is advantageous in keeping the performance of the automobile C constant. 
     Moreover, by using the external sensor such as the external air temperature sensor SW 1 , such control that a change in the performance of the unit  20  is associated with the operation environment of the automobile C can be achieved. Accordingly, the performance of each unit  20  can be more properly compensated. 
     Other Embodiments 
     (Other Units  20 ) 
     In the above-described embodiment, the control associated with the combination of the engine as the first unit  20   1  and the motor as the second unit  20   2  has been described. However, the present disclosure is not limited to such control. The present disclosure is also applicable to control associated with the combination of the brake unit with the engine and the motor. Similarly, the present disclosure is also applicable to control associated with the combination of the steering unit and the brake unit instead of the engine and the motor. 
     (Cooperation with External Server Cs) 
     In the above-described embodiment, the configuration has been described, in which the PCM  100  of each automobile C forming the control system S functions as the control apparatus of the present disclosure, but the present disclosure is not limited to such a configuration. At least some of the functional blocks functioning as the control apparatus may be mounted on the external server Cs, and the automobiles C may communicate with each other via the external server Cs. In this case, a calculation system with the combination of the PCM  100  and the external server Cs functions as the control apparatus of the present disclosure. 
     In this case, as in a PCM  100 ′ shown in  FIG. 11 , the first characteristic estimator  10   1  to the N-th characteristic estimator  10   N  can be mounted on the external server Cs. The configuration is not limited to the illustrated example, and some of the first characteristic estimator  10   1  to the N-th characteristic estimator  10   N  may be mounted on the PCM  100 ′ and the other estimators may be mounted on the external server Cs, or a functional block other than the first characteristic estimator  10   1  to the N-th characteristic estimator  10   N , such as the plant behavior estimator  11 , may be mounted on the external server Cs. 
     (Cooperation Between Plants) Instead of the configuration shown in  FIG. 11 , a configuration may be employed, in which the specifying result of the unit specifier (the characteristic estimator  10 ) in any one of the plants is shared among the other plants. In this case, as shown in  FIG. 12 , the characteristic estimator  10  is mounted only on a predetermined PCM  100   1 ″, and the other PCM  100   2 ″ performs, e.g., correction of the target characteristic in response to a specifying result obtained by the PCM  100   1 ″. In this case, cooperation via the external server Cs is not essential. 
     The configuration is limited to the illustrated example, and in a state in which the characteristic estimator  10  is also mounted on the PCM  100   2 ″, information on, e.g., the unit whose performance has changed is mutually exchanged between the plants. For example, a database, a map, a model, and other factors generated based on the external air temperature can be shared among the automobiles C. 
     (Cooperation with Factories F 1 , F 2 ) 
     For example, as shown in  FIG. 13 , instead of or in addition to cooperation of the automobiles C with each other via the external server Cs, the automobile C, the component factory F 1  for the automobile C, and the system repair factory F 2  for the automobile C can cooperate with each other. 
     In this case, as shown in a process P 1 , when information indicating the knowledge obtained by the automobile C (more specifically, information indicating a change in the unit performance of each unit  20  over time) is transmitted to the external server Cs, the external server Cs orders the component factory F 1  to manufacture the unit  20  or orders the component factory F 1  to manufacture the sub-units forming each unit  20 , such as the throttle valve  201   a  and the EGR valve  201   b , based on a change in the unit performance over time (see a process P 2 ). 
     Thereafter, as shown in a process P 3  and a process P 4 , components such as the sub-units are delivered from the component factory F 1  to the system repair factory F 2 , and the delivery of the components is notified from the component factory F 1  to the external server Cs. Thereafter, the external server Cs reserves maintenance work in the system repair factory F 2  (see a process P 5 ). Finally, the system repair factory F 2  or the external server Cs notifies the automobile C of the contents of the reservation (see a process P 6 ). 
     As described above, the control apparatus of the present disclosure performs the control based on a change in the unit performance, and becomes extremely useful by outputting the information indicating such a change to the outside of the plant or sharing such information among the plants.