Patent ID: 12248283

EXAMPLE EMBODIMENT

For clarity of explanation, the following descriptions and drawings will be appropriately omitted and simplified. Further, the respective components described in the drawings as functional blocks which perform various kinds of processing can be configured by Central Processing Units (CPUs), memories or other circuits in terms of hardware, and are achieved by programs loaded in memories, or the like in terms of software. Accordingly, it will be understood by those skilled in the art that these functional blocks can be implemented in various forms by only hardware, only software or a combination thereof. They are not limited to any of them. Incidentally, in the respective drawings, the same components are denoted by the same reference numerals, and dual description will be omitted as needed.

Further, the above-described program can be stored and provided to a computer using any type of non-transitory computer readable media. Non-transitory computer readable media include any type of tangible storage media. Examples of non-transitory computer readable media include magnetic storage media (such as flexible disks, magnetic tapes, hard disk drives, etc.), optical magnetic storage media (e.g., magneto-optical disks), CD-Read Only Memory (CD-ROM), CD-R, CD-R/W, and semiconductor memories (such as mask ROM, Programmable ROM (PROM), Erasable PROM (EPROM), flash ROM, Random Access Memory (RAM), etc.). The program may be provided to a computer using any type of transitory computer readable media. Examples of transitory computer readable media include electric signals, optical signals, and electromagnetic waves. Transitory computer readable media can provide the program to a computer via a wired communication line (e.g., electric wires, and optical fibers) or a wireless communication line.

First Example Embodiment

Hereinafter, with reference to the drawings, example embodiments of the present invention will be described. A work control method, a work control system, and a work control apparatus of a construction machine described below control a construction machine that drives joints of a machine using a cylinder. The following description will be made taking a backhoe as an example of the construction machine. Further, while a work control system in which process blocks that perform work control processing are arranged in a plurality of places in a distributed manner via a network will be described in the following description, a work control apparatus in which the process blocks included in the work control system are formed of one apparatus may be employed. Further, the content of the control performed in the work control system will be referred to as a work control method.

Further, the work control system that will be described below may be applied to a machine having a manipulation lever that can be operated by a worker as a construction machine or may be applied to a machine that directly controls a drive mechanism using, for example, an electromagnetic proportional valve by an electrical signal without using a manipulation lever.

FIG.1shows a schematic diagram of a construction machine controlled by a work control system1according to the first example embodiment. A construction machine10shown inFIG.1is a backhoe. The construction machine includes a crawler11, a turning base12, a cockpit13, a boom14, an arm15, and a bucket16. The crawler11is a caterpillar for moving the construction machine10. The turning base12turns a chassis on which the cockpit13, the boom14and the like are mounted. The cockpit13is a manipulation room in which a manipulation lever and the like for manipulating the posture of the construction machine10are disposed. Further, while the drawings are omitted, in the work control system1, a construction machine drive processing unit17is disposed in the construction machine10. Further, each of the boom14, the arm and the bucket16corresponds to a movable part and is operated by a hydraulic cylinder. This hydraulic cylinder is elongated or contracted by an action of the construction machine drive processing unit17. Note that the part that corresponds to the movable part includes, for example, besides the hydraulic cylinder, a part that is driven by the motor.

Note that the construction machine drive processing unit17may operate, for example, an actuator that displaces a manipulation lever operable by a worker or may operate an electromagnetic proportional valve or the like by an electrical signal.

The work control system1according to the first example embodiment provides a feedback control input value for the construction machine drive processing unit17of the construction machine10, thereby moving the movable parts such as the boom14of the construction machine10. Then, the work control system1according to the first example embodiment performs feedback control while adjusting the control gain used in feedback control for each predetermined control section. In the following, the work control system1according to the first example embodiment will be described in detail.

First, a configuration of a process block of the work control system1according to the first example embodiment will be described.FIG.2shows a schematic block diagram of the work control system according to the first example embodiment. The construction machine10is shown inFIG.2as a target to be controlled by the work control system1. In the example shown inFIG.2, the posture control apparatus20is provided with a construction machine control unit21and a posture detection unit22. The work control apparatus30is provided with a control parameter adjustment unit31and a feedback control unit32. The construction machine10is manipulated using the posture control apparatus20and the work control apparatus30. The example shown inFIG.2is merely one example. For example, the posture control apparatus20and the work control apparatus30may be integrated as one apparatus and the construction machine10and the posture control apparatus20may be connected to each other by communication. Further, the posture control apparatus20may be provided in such a way that the posture control apparatus20and the construction machine10are integrated with each other to obtain a form in which the posture control apparatus20and the work control apparatus30are connected to each other by communication. Further, the construction machine10is a target to be controlled by the work control apparatus30and the posture control apparatus20may be an interface for allowing the work control apparatus30to actually operate the construction machine10. In this case, it can be considered that the work control apparatus30is a main part of the work control system1.

The posture control apparatus20includes the construction machine control unit21and the posture detection unit22. The construction machine control unit21provides a feedback control input value computed by the feedback control unit32for the construction machine drive processing unit17, thereby operating the movable part of the construction machine10. The posture detection unit22acquires joint angles of the respective movable parts from sensors provided in the movable parts such as the arm of the construction machine and outputs the acquired joint angles as posture detection values indicating the posture of the construction machine10.

The work control apparatus30includes the control parameter adjustment unit31and the feedback control unit32. The control parameter adjustment unit31adjusts the control gain for each control section, which is a unit section of control. Further, the control parameter adjustment unit31adjusts the control gain for each control section based on the posture detection value detected by the posture detection unit22. The details of the processing of adjusting the control gain will be described later. The feedback control unit32computes the feedback control input value for controlling the posture of the construction machine using the control gain computed by the control parameter adjustment unit31and the posture detection value acquired from the posture detection unit22. The feedback control unit32performs processing of generating the feedback control input value by PID control or the like using the posture detection value.

Note that the feedback control input value may be generated for each of the movable parts of the construction machine10or may include input values for the plurality of movable parts. It is further assumed that the work control system1computes an input value using parameters that are different from each other for each movable part.

FIG.3shows a detailed block diagram of the work control system1according to the first example embodiment.FIG.3shows the construction machine10, the construction machine control unit21, and the posture detection unit22already described above in order to indicate a flow of information exchanged between blocks. As shown inFIG.3, the work control apparatus30includes the control parameter adjustment unit31, the feedback control unit32, and a work instruction unit33. The work instruction unit33provides a work instruction indicating the content of the work to be performed by the construction machine10for the control parameter adjustment unit31and the feedback control unit32. In the following, in particular, the control parameter adjustment unit31and the feedback control unit32will be described in detail.

The control parameter adjustment unit31includes an overshoot computation unit311, an addition/subtraction rate computation unit312, an addition/subtraction rate smoothing processing unit313, and a control gain computation unit314. The overshoot computation unit311computes an amount of overshoot of a posture detection valve with respect to a target position in a previous control section. This posture detection value is output from the posture detection unit22. The addition/subtraction rate computation unit312computes a control gain addition/subtraction rate, which is an addition/subtraction rate of the control gain in the next control section, based on the amount of overshoot.

The addition/subtraction rate smoothing processing unit313computes a post-smoothing addition/subtraction rate in which the control gain addition/subtraction rate is smoothed using the smoothing coefficient switched based on an increasing/decreasing direction of the control gain addition/subtraction rate determined by the post-smoothing addition-subtraction rate computed in the previous control section and the control gain addition/subtraction rate computed by the addition/subtraction rate computation unit312. The control gain computation unit314computes the control gain in the next control section from the post-smoothing addition/subtraction rate.

FIG.4shows a more detailed block diagram of the addition/subtraction rate smoothing processing unit313. As shown inFIG.4, the addition/subtraction rate smoothing processing unit313includes a smoothing coefficient decision unit41and a post-smoothing addition/subtraction rate computation unit42. The smoothing coefficient decision unit41rewrites, when the control gain addition/subtraction rate is larger than the post-smoothing addition/subtraction rate computed in the previous control section, the smoothing coefficient in such a way that the smoothing coefficient becomes a smaller value, and outputs the smoothing coefficient.

The work control system1according to the first example embodiment treats, as the smoothing coefficient, a combination of a large value and a small value as one set. Further, the work control system1according to the first example embodiment holds a plurality of sets of smoothing coefficients in accordance with the difference in the control target position or the content of the work instruction in a system in advance.

The post-smoothing addition/subtraction rate computation unit42performs smoothing processing in which the smoothing coefficient decided by the smoothing coefficient decision unit41is applied to the control gain addition/subtraction rate that corresponds to the previous control section and the control gain addition/subtraction rate that corresponds to the next control section, and thus computes the post-smoothing addition/subtraction rate.

The feedback control unit32includes an error update unit321and a control input computation unit322. The error update unit321computes an error between the target position included in the instruction indicating the content of the work obtained from the work instruction unit33and the posture detection value obtained from the posture detection unit22. The control input computation unit322computes the feedback control input value for controlling the posture of the construction machine using the control gain computed by the control gain computation unit314. At this time, the control input computation unit322computes the feedback control input value in such a way that the error computed by the error update unit321is made close to zero.

The operation of the above-mentioned process block will be described in more detail. In the following, an example in which a period from when the target position is set to when it is changed next time is set as the control section will be described. Further, in the following description, one of the control target positions is targeted. In the work control system1according to the first example embodiment, the operation that will be described below is performed for each control target position.

First, overshoot computation processing performed by the overshoot computation unit311will be described.FIG.5shows a flowchart for describing overshoot computation processing according to the first example embodiment. As shown inFIG.5, in the overshoot computation processing according to the first example embodiment, first, the direction of the overshoot is computed from the difference between the initial position of the control section and the target position (Step S1). Next, the error of the current position of the control target position grasped from the posture detection value and the target position with respect to the direction of the overshoot is computed (Step S2). Next, the maximum error from the initial time of the control section to the current time is computed (Step S3). Then, the processing of Steps S2and S3is repeated until the target position is switched (Step S4). When it is determined in this Step S4that the target position has been switched, the overshoot computation unit311computes the maximum error detected through Steps S2-S4as the amount of overshoot in the previous control section (Step S5).

The flowchart shown inFIG.5will be described using a timing chart indicating the change in the current position.FIG.6shows a timing chart for describing the magnitude of overshoot addressed in the overshoot computation processing. As shown inFIG.6, in the first example embodiment, the control section is switched every time the target position is switched. For example, in the example shown inFIG.6, a period from a time t1(j) when θT(i) is set as the target position to a time t2(j) is set to be a control section j.

The overshoot computation unit311determines, in the computation of the direction of the overshoot in Step S1, the position of the control target position of the start time of the control section based on the difference between θ(t1(j)) and the target position θT(i) in the control section j. The overshoot computation unit311further computes, in Step S2, the error in the direction determined in Step S1. The overshoot computation unit311further continuously acquires the local maximum value of the overshoot in the direction that is the same as the direction in which the target position changes during the control section. When the error with respect to the target position θT(i) is denoted by ei(t), the error ei(t) is expressed by Expression (1). In Step S3, the error e(i) is accumulated every time the local maximum value of the overshoot occurs.

[Expression⁢1]ei(t)={max⁢{θ⁡(t)-θ⁢T⁡(i),0}if⁢θ⁡(t⁢1⁢(j))≤θ⁢T⁡(i)max⁢{θ⁢T⁡(i)-θ⁡(t),0}others(1)

After that, at a timing when the control section is ended, the overshoot computation unit311computes, using Expression (2), the maximum value a(j) of the error during the control period j (the period from t1(j) to t2(j)) and computes the computed maximum value as the amount of overshoot a(j).
[Expression 2]
a(j)=supei(t)t∈[t1(j),t2(j)]  (2)

Next, an operation of the addition/subtraction rate computation unit312according to the first example embodiment will be described in detail.FIG.7shows a flowchart for describing addition/subtraction rate computation processing according to the first example embodiment. As shown inFIG.7, the addition/subtraction rate computation unit312acquires the amount of overshoot in the previous control section computed by the overshoot computation unit311(Step S11). Next, the addition/subtraction rate computation unit312acquires the content of the current work from the work instruction unit33(Step S12). After that, the addition/subtraction rate computation unit312computes the control gain addition/subtraction rate with respect to the content of the current work from the amount of overshoot in the previous control section (Step S13).

When the amount of overshoot is denoted by a(j), a weight coefficient set to have a desired magnitude is denoted by to, and the control gain addition/subtraction rate that corresponds to the control section j is denoted by r(j), the control gain addition/subtraction rate can be expressed by Expression (3).
[Expression 3]
r(j)=1+ω·a(j)  (3)

Next, an operation of the smoothing coefficient decision unit41according to the first example embodiment will be described in detail.FIG.8shows a flowchart for describing the smoothing coefficient decision processing according to the first example embodiment. As shown inFIG.8, the smoothing coefficient decision unit41acquires the control gain addition/subtraction rate computed by the addition/subtraction rate computation unit312(Step S21). Next, the smoothing coefficient decision unit41acquires the post-smoothing addition/subtraction rate in the previous control section from the post-smoothing addition/subtraction rate computation unit42(Step S22). Then, the smoothing coefficient decision unit41compares the magnitude of the control gain addition/subtraction rate acquired in Step S21and that of the post-smoothing addition/subtraction rate acquired in Step S22(Step S23).

When the control gain addition/subtraction rate is larger than the post-smoothing addition/subtraction rate in Step S23, the smoothing coefficient decision unit41determines that the addition/subtraction rate is increasing and sets the smoothing coefficient α when the increase rate increases to be the smoothing coefficient when the increase rate increases to be used to compute the control gain in the next control section (Step S24). On the other hand, when the control gain addition/subtraction rate is equal to or smaller than the post-smoothing addition/subtraction rate in Step S23, the smoothing coefficient decision unit41determines that the addition/subtraction rate is decreasing and sets the smoothing coefficient β when the increase rate decreases to be the smoothing coefficient when the increase rate increases to be used to compute the control gain in the next control section (Step S25). The smoothing coefficient α and the smoothing coefficient β have a relation α<β.

Next, an operation of the post-smoothing addition/subtraction rate computation unit42according to the first example embodiment will be described in detail.FIG.9shows a flowchart for describing the smoothing addition/subtraction rate computation processing according to the first example embodiment. As shown inFIG.9, the post-smoothing addition/subtraction rate computation unit42acquires the smoothing coefficient computed in the smoothing coefficient decision unit41(Step S31). Further, the post-smoothing addition/subtraction rate computation unit42acquires the control gain addition/subtraction rate computed by the addition/subtraction rate computation unit312(Step S32). Then, the post-smoothing addition/subtraction rate computation unit42computes the post-smoothing addition/subtraction rate in the next control section using the values acquired in Steps S31and S32(Step S33).

In the work control system1according to the first example embodiment, the smoothing coefficient computed in the smoothing coefficient decision unit41varies depending on the increasing/decreasing direction of the control gain addition/subtraction rate. The post-smoothing addition/subtraction rate computed in Step S33is computed either by Expression (4) or Expression (5) depending on the difference in the increasing/decreasing direction of the control gain addition/subtraction rate. Expression (4) is an expression when the control gain addition/subtraction rate increases and Expression (5) is an expression when the control gain addition/subtraction rate decreases. Note that R(j) is a post-smoothing addition/subtraction rate in the control section j and R(j+1) is a post-smoothing addition/subtraction rate in the control section j+1, which is the next control section. Further, the post-smoothing addition/subtraction rate R(1) in the control section when the construction machine10starts operating is 1.
[Expression 4]
R(j+1)=α·R(j)+(1−α)·r(j)  (4)
[Expression 5]
R(j+1)=β·R(j)+(1−β)·r(j)  (5)

Now, a relation between the amount of overshoot and the smoothing addition/subtraction rate will be described.FIG.10shows a graph describing a relation between the amount of overshoot and the smoothing addition/subtraction rate. In the graph shown inFIG.10, the processing is repeatedly executed for 10 control sections using the control parameter adjustment unit31according to the first example embodiment. In the graph inFIG.10, the horizontal axis shows the number of control sections where the attempts have been repeated (the number of attempts), the vertical axis on the left side shows the amount of overshoot, and the vertical axis on the right side shows the post-smoothing addition/subtraction rate. Further,FIG.10shows the amount of overshoot by a solid line and the post-smoothing addition/subtraction rate by an alternate long and short dash line. Further, in the example shown inFIG.10, the smoothing coefficient α where the amount of overshoot is large and that is selected in the direction in which the control gain addition/subtraction rate is increasing is set to be 0.8, and the smoothing coefficient β where the amount of overshoot is small and that is selected in the direction in which the control gain addition/subtraction rate is decreasing is set to be 0.99.

In the example shown inFIG.10, in the attempt period in which the number of attempts is one or two times, overshoot equal to or larger than a certain value continuously occurs. Therefore, the smoothing addition/subtraction rate to be applied to the control gain that corresponds to the second time and the third time significantly increases. Accordingly, the control gain decreases in the direction in which the amount of overshoot is suppressed.

Further, in the attempt period in which the number of attempts is three to five times, the amount of overshoot is suppressed to be equal to or smaller than a certain value. Therefore, the smoothing addition/subtraction rate to be applied to the control gain that corresponds to the fourth to sixth times gradually decreases. Accordingly, the operation speed of the construction machine10is maintained while the amount of overshoot is maintained so that it is suppressed to be equal to or smaller than the certain value.

Further, in the attempt period in which the number of attempts is six times, the amount of overshoot exceeds the certain value. Therefore, the smoothing addition/subtraction rate applied to the control gain that corresponds to the seventh attempt significantly increases. Accordingly, the control gain decreases in the direction in which the amount of overshoot is suppressed.

Further, in the attempt period in which the number of attempts is seven to ten times, the amount of overshoot is reduced to be equal to or smaller than the certain value. Therefore, the smoothing addition/subtraction rate to be applied to the control gain that corresponds to the eighth to eleventh times (the eleventh time is not shown) gradually decreases. Accordingly, the operation speed of the construction machine10is maintained while the amount of overshoot is maintained so that it is suppressed to be equal to or smaller than the certain value.

As described above, the work control system1according to the first example embodiment smooths the addition/subtraction rate to be applied to the computation of the control gain using the addition/subtraction rate computation unit312, the smoothing coefficient decision unit41, and the post-smoothing addition/subtraction rate computation unit42, thereby adjusting the control gain in such a way that the control gain gradually increases when the amount of overshoot is small while immediately suppressing the amount of overshoot so that it is equal to or smaller than the certain value.

Next, the control gain computation unit314will be described.FIG.11shows a flowchart for describing control gain computation processing according to the first example embodiment. As shown inFIG.11, the control gain computation unit314first acquires the latest post-smoothing addition/subtraction rate computed by the post-smoothing addition/subtraction rate computation unit42(Step S41). Next, the control gain computation unit314computes the control gain in the next control section using the post-smoothing addition/subtraction rate acquired in Step S41(Step S42).

Now, the control gain computation processing in the control gain computation unit314will be described in further detail. In this example, the previous control section in which the maximum value of the amount of overshoot is acquired is denoted by j and the control section in which the control gain computed based on the result of the previous control section j is applied is set to be the next control section j+1. Further, the control gain that corresponds to the next control section j+1 is denoted by K(j+1), the initial value of the control gain is denoted by K(1), and the smoothing addition/subtraction rate that is computed based on the result of the previous control section j and is to be applied to the next control section j+1 is denoted by R(j+1). Under these conditions, the control gain computation unit314computes the control gain K(j+1) to be applied to the next control section j+1 based on Expression (6).
[Expression 6]
K(j+1)=K(1)/R(j+1)  (6)

Next, processing of computing the feedback control input value in the feedback control unit32will be described. The feedback control unit32includes an error update unit321and a control input computation unit322. Then, the error update unit321computes an error between the posture detection value in real time and the target position. Then, the control input computation unit322computes a feedback control input value for making the error close to zero. The processing of computing the feedback control input value in the control input computation unit322will be described.FIG.12shows a flowchart for describing the feedback control processing according to the first example embodiment.

As shown inFIG.12, the control input computation unit322first acquires the control gain computed by the control gain computation unit314(Step S51). Next, the control input computation unit322computes a feedback control input value using the acquired control gain (Step S52). That is, the feedback control unit32computes the feedback control input value based on the control gain updated by the control parameter adjustment unit31.

From the above description, the work control system1according to the first example embodiment adjusts the magnitude of the control gain to be applied to the next control section based on the amount of overshoot that has occurred in the previous control section for each control section. That is, the work control system1according to the first example embodiment adjusts the control gain in accordance with the torque of each position or the content of the work that is changed during the operation of the construction machine10. The content of the work includes, for example, extending the arm to an excavation site, inserting the cutting edge of the bucket into the excavation site, excavating, lifting, changing directions with the excavated earth and sand on the bucket, or releasing the earth and sand in the bucket. In these operations, the torque for moving the bucket or the arm in a state in which the bucket is filled with earth and sand is different from the torque for moving the bucket or the arm in a state in which the bucket is not filled with earth and sand. Further, the torque required during the excavation work is different from the torque required during other work. In the construction machine, the torque required for each part varies depending on the content of the work. The control gain is computed for each control section based on the amount of overshoot derived in the previous control section, like in the work control system1according to the first example embodiment. Accordingly, in the work control system1according to the first example embodiment, it is possible to reduce the amount of overshoot even when the torque required for each part increases or decreases.

Further, the work control system1according to the first example embodiment selects one of the smoothing coefficient α and the smoothing coefficient β by the post-smoothing addition/subtraction rate computation unit42in accordance with the result of comparing the smoothing addition/subtraction rate computed in the previous control section with the control gain addition/subtraction rate computed from the amount of overshoot that has occurred in the previous control section. Then the relation between the smoothing coefficient α and the smoothing coefficient β is set to be α<β. Accordingly, the work control system1according to the first example embodiment increases the sensitivity of the control gain in the decreasing direction and decreases the sensitivity of the control gain in the increasing direction. By performing this control, in the work control system1according to the first example embodiment, it is possible to perform control in such a way that the operation speed of the construction machine10is not unreasonably reduced while rapidly suppressing the magnitude of overshoot so that it is equal to or smaller than the certain value.

Further, the work control system1according to the first example embodiment switches the combination of smoothing coefficients selected by the post-smoothing addition/subtraction rate computation unit42in accordance with the part of the target to be controlled or the content of the work. Accordingly, the work control system1according to the first example embodiment is able to compute the optimal control gain in accordance with the content of the work or the required torque.

Second Example Embodiment

In a second example embodiment, another form of the method for setting the control sections will be described. In the first example embodiment, only one switch of target positions occur in one control section. In the second example embodiment, a plurality of switches of target positions occur in one control section. A method of computing an amount of overshoot when the switches of target positions occur will be described.

FIG.13shows a timing chart for describing a relation between the control section and the target position according to the second example embodiment. In the example shown inFIG.13, four target position switches occur in a control section j from a time t1(j) to a time t2(j). The amounts of the overshoot that occur in the four target position switches are respectively denoted by a(i)-a(i+3). The amounts of overshoot a(i)-a(i+3) are computed in accordance with Expression (1). In the second example embodiment, the amounts of overshoot are computed in accordance with Expression (7) or (8) in place of Expression (2). Expression (7) is an expression in which the average value of the amounts of overshoot a(i)-a(i+3) that occur in the control period j is set to be the amount of overshoot a(j) in the control period. Expression (8) is an expression in which the maximum value of the amounts of overshoot a(i)-a(i+3) that occur in the control period j is set to be the amount of overshoot a(j) in the control period. In Expressions (7) and (8), n and k indicate the number of switches of the target value in one control period.

[Expression⁢7]a⁡(j)=1n⁢∑k=0n-1a⁡(i+k)(7)[Expression⁢8]a⁡(j)=max⁢{a⁡(i),a⁡(i+1),…,a⁡(n-1)}(8)

From the above description, in the second example embodiment, the length of the control section may be set in a desired way and the period during which the control gain of the work control system1according to the first example embodiment is adjusted can be set in a flexible manner.

While the present invention has been described above with reference to the example embodiments, the present invention is not limited to the example embodiments. Various changes that can be understood by those skilled in the art within the scope of the present invention can be made to the configurations and the details of the present invention.

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-162900, filed on Sep. 29, 2020, the disclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

1Work Control System10Construction Machine11Crawler12Turning Base13Cockpit14Boom15Arm16Bucket17Construction Machine Drive Processing Unit181-184Posture Sensor20Posture Control Apparatus21Construction Machine Control Unit22Posture Detection Unit30Work Control Apparatus31Control Parameter Adjustment Unit32Feedback Control Unit311Overshoot Computation Unit312Addition/subtraction Rate Computation Unit313Addition/subtraction Rate Smoothing Processing Unit314Control Gain Computation Unit321Error Update Unit322Control Input Computation Unit33Work Instruction Unit41Smoothing Coefficient Decision Unit42Post-smoothing Addition/subtraction Rate Computation Unit