In recent years, the double-layered multi-head weighers whose hoppers are arranged in two levels are widely used in the accurate and reliable weighing for packing food products. The weighing processes are mathematically modeled into a single objective optimization problems. The objective of packing problem is to minimize the total weight of combined hoppers for a package under the condition that the total weight must be no less than a specified target weight. This paper proposes a novel single objective optimization approach for double-layered multi-head weighing process. More precisely, relying on a new bound on the optimal weight, this study accurately determines the number of hoppers to be combined at each packing operation, and find the best possible hopper combination using the single-objective algorithm. This method significantly speeds up the packing process as a whole. According to the present approach, the candidate number of hoppers to be combined can be taken one or two integral values. The probability that the accurate number of hoppers to be combined becomes one integral value is explicitly calculated, which is the performance factor to the previous one. In addition, results from the numerical experiments to show the effectiveness of the proposed approach are presented.
| Published in | Mathematical Modelling and Applications (Volume 9, Issue 3) |
| DOI | 10.11648/j.mma.20240903.12 |
| Page(s) | 61-69 |
| Creative Commons |
This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited. |
| Copyright |
Copyright © The Author(s), 2024. Published by Science Publishing Group |
Double Layer, Multi-Head Weigher, Packaging Process, Optimization, Single Objective Problem
weighing hoppers, a set of
booster hoppers and a discharge chute to the packaging machine (see Figure 1 and Figure 2). Each weighing hopper has its own highly accurate load cell. This load cell will calculate the weight of product in the weighing hopper. The booster hoppers are nothing but the ordinary hoppers without load cell. They are placed underneath of weighing hoppers uprightly or diagonally based on the constructional feature of machine, according to which distinguish the double-layered multi-head weighers upright from diagonal. The packing process begins when the food product is fed into the top of the multi-head weigher, where a dispersal system, normally a vibrating or rotating top cone, distributes the product into a series of linear or radial feeder plates. This top cone is normally equipped with a load cell which controls the feed of product to the multi-head weigher. The linear or radial feeder plates vibrate individually and deliver the food product into the set of
weighing hoppers. The set of weighing hoppers send the food product into the set of
booster hoppers. After each delivery to the weighing and booster hoppers, the linear or radial feeders will stop vibrating and wait until the weighing hoppers have emptied their contents into the booster hoppers before starting again.
weighing hoppers and
booster hoppers to achieve the desired target weight
, and chooses some hoppers from the total
hoppers for a package. Once the calculation is completed, it will open the combined hoppers (hereafter, denote by
this subset, i.e.
) and discharge the accurately weighed portion into the packing system or product trays. The resulting empty weighing hoppers (i.e.
) are supplied with next new contents of product, and such a packing operation is repeated continuously to produce a large number of food packages one by one.
. It is a common knowledge that the number of possible different hopper subsets to be combined is different at each packing operation. This optimization problem that minimize the difference between the combined and the target package weight is known as the NP-complete subset-sum combinatorial one
are the real weights of food contents feeded in the weighing hoppers and
denotes the normal distribution whose mean is
and standard deviation is
. In the sequel, this paper uses the cumulative distribution function
of normal distribution defined by
. Since all the weights are independently and identically distributed, the total weight of randomly selected
hoppers follows a normal distribution
. Thus, One might expect that the average package mean weight
equals to the target weight
, that is, the number of hoppers
to be combined at each packing operation is constant and fixed in advance, where
is determined by
. One might call such
hopper combination are valid hopper combination. Afterawards
to be combined has previously been defined. However, there is an important problem for choosing
in the industrial setting. Although the weights of food product in the hoppers follow the normal distribution, the average package mean
of food product is not the same for all the types of food products. Morever,
is not always integer in general. For example, if one packs some food product whose target weight
is
and average package mean
is
, then the candidate number
of hoppers to be combined becomes
. In such case, it is natural to choose
and
. In other words, one must find the optimal weight among both
and
hopper combinations. It will reduce the computational time if it is proved that only
hopper or only
hopper combinations are valid. The computational cost of generating and evaluating all the valid hopper combinations is closely related to the accurate determination of the number of hoppers to be combined from the candidate numbers. This problem becomes more difficult when the entire number of hoppers are large, especilly when the double-layered multihead weighing process work.
: Set of total
hoppers.
: The total number of packages needed.
: Current iteration number of packing operation.
: The weights of food product in the weighing hoppers at
-th packing operation.
: The weights of food product in the booster hoppers at
-th packing operation.
: Set of all hopper combinations at
-th packing operation.
: The total weight calculated as the sum of the weight in
hoppers at
-th packing operation.
: Target weight.
of combinations for the upright type double-layered weighing process when the fixed
hoppers are combined is calculated by
(1)
] denotes the integer part of
. It was also proved in
of combinations for the diagonal type double-layered weighing process when the fixed
hoppers are combined is computed by
(2)
at every packing operation such that some weight
is minimized under the condition that
. The
-dimensional binary vectors
is defined as follows.
is formulated as follows.
(3)
(4)
(5)
(6)
of (3) aims at attaining the total weight of selected hoppers as close to the target weight
as possible, under the condition (4) (i.e., the target weight constraint). The equation (5) reflects the constructional feature of upright type that it cannot choose the
-th weighing hopper unless it chooses the
-th booster hopper. A solution
satisfying (4)-(6) is referred to as a feasible solution of the problem
. Moreover, for the problem
,
is denoted by the minimum of the total weight of a feasible solution
. An optimal solution
is defined as a feasible solution satisfying
.
is formulated as follows.
(7)
(8)
(9)
(10)
of (7) aims at attaining the total weight of selected hoppers as close to the target weight
as possible, under the condition (8) (i.e., the target weight constraint). The equation (9) reflects the constructional feature of diagonal type that it cannot choose the
-th weighing hopper unless it chooses the
-th booster hopper. A solution
satisfying (8)-(10) is referred to as a feasible solution of the problem
. Moreover, for the problem
,
is denoted the minimum of the total weight of a feasible solution
. An optimal solution
is defined as a feasible solution satisfying
.
be the optimal solution that satisfies
for both problems
and
. Then it holds that
(11)
is proved. Since the optimal solution
is a feasible one with the target weight constraint (4), the left hand side inequality of (11) holds. By the optimality of
, it holds that
(12)
. If the converse inequality
holds, then it implies that deleting
from the optimal solution becomes another feasible solution, and it contradicts the optimality of
. Similarly, it also holds that
(13)
is proved. Since the optimal solution
is a feasible one with the target weight constraint (8), the left hand side inequality of (11) also holds for the problem
. By the optimality of
, it holds that
(14)
. If the converse inequality
holds, then it implies that deleting
from the optimal solution becomes another feasible solution for the problem
, and it contradicts the optimality of
. In the similar fashion as above, it also holds that
(15)
. Therefore, the right hand side inequality of (11) holds for the problem
. Finally, the theorem is proved.
hoppers follow independently and identically a normal distribution
(16)
is the average package weight and
is the standard deviation. Garcia-Diaz et al.
to be combined at each packing operation is constant and fixed in advance, where
is determined by
and the set of all possible
-hopper combinations becomes valid hopper combinations. As already mentiond in section 1,
is not always integer for any
and
. It is hard to fix
such that
becomes an integer in the real industrial settings.
(17)
is defined in detail.
if
(18)
and
if
(19)
denotes the integer part of
.
is explicitly calculated. This probability is computed by (18) and using the property of extreme distribution
(20)
is the cumulative distribution function of normal distribution. From (20), one concludes that this probability increases when the total number of hoppers
increases.
.
, then one has from Figure 3 that
(21)
, then one has from Figure 3 that
(22)
, then one has from Figure 3 that
(23)
-Total number of hoppers,
-Number of hoppers involved in each packing operation (
),
-Target weight (
),
-Total number of packages to be produced,
-Iteration number of packing (
),
-Average package weight of food product,
-Standard deviation of the weights supplied to each hopper.
and
for all
.
.
is assigned.
of hoppers to be combined as follows.
hopper combinations. If sum weight is less than the target weight
, then delete this combination from
.
packets has been completed, the process ends. Otherwise, it returns to Step 3.
, the total weight
, the average package mean
and the total number of packages to be produced
. Then the candidate number of valid hopper
is calculated by
-hopper combinations and
-hopper combinations at every packing, i.e. the total number of combinations is computed by (1) and (2), respectively.
(24) min | Minimize |
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APA Style
An, P., Hong, C., Ri, R., Yu, C., O, C. (2024). An Improved Single Objective Optimization Approach for Double-Layered Multi-Head Weighing Process. Mathematical Modelling and Applications, 9(3), 61-69. https://doi.org/10.11648/j.mma.20240903.12
ACS Style
An, P.; Hong, C.; Ri, R.; Yu, C.; O, C. An Improved Single Objective Optimization Approach for Double-Layered Multi-Head Weighing Process. Math. Model. Appl. 2024, 9(3), 61-69. doi: 10.11648/j.mma.20240903.12
AMA Style
An P, Hong C, Ri R, Yu C, O C. An Improved Single Objective Optimization Approach for Double-Layered Multi-Head Weighing Process. Math Model Appl. 2024;9(3):61-69. doi: 10.11648/j.mma.20240903.12
@article{10.11648/j.mma.20240903.12,
author = {Pom An and Chol-Jun Hong and Ryong-Yon Ri and Chol-Jun Yu and Chol-Jun O},
title = {An Improved Single Objective Optimization Approach for Double-Layered Multi-Head Weighing Process
},
journal = {Mathematical Modelling and Applications},
volume = {9},
number = {3},
pages = {61-69},
doi = {10.11648/j.mma.20240903.12},
url = {https://doi.org/10.11648/j.mma.20240903.12},
eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.mma.20240903.12},
abstract = {In recent years, the double-layered multi-head weighers whose hoppers are arranged in two levels are widely used in the accurate and reliable weighing for packing food products. The weighing processes are mathematically modeled into a single objective optimization problems. The objective of packing problem is to minimize the total weight of combined hoppers for a package under the condition that the total weight must be no less than a specified target weight. This paper proposes a novel single objective optimization approach for double-layered multi-head weighing process. More precisely, relying on a new bound on the optimal weight, this study accurately determines the number of hoppers to be combined at each packing operation, and find the best possible hopper combination using the single-objective algorithm. This method significantly speeds up the packing process as a whole. According to the present approach, the candidate number of hoppers to be combined can be taken one or two integral values. The probability that the accurate number of hoppers to be combined becomes one integral value is explicitly calculated, which is the performance factor to the previous one. In addition, results from the numerical experiments to show the effectiveness of the proposed approach are presented.
},
year = {2024}
}
TY - JOUR T1 - An Improved Single Objective Optimization Approach for Double-Layered Multi-Head Weighing Process AU - Pom An AU - Chol-Jun Hong AU - Ryong-Yon Ri AU - Chol-Jun Yu AU - Chol-Jun O Y1 - 2024/09/06 PY - 2024 N1 - https://doi.org/10.11648/j.mma.20240903.12 DO - 10.11648/j.mma.20240903.12 T2 - Mathematical Modelling and Applications JF - Mathematical Modelling and Applications JO - Mathematical Modelling and Applications SP - 61 EP - 69 PB - Science Publishing Group SN - 2575-1794 UR - https://doi.org/10.11648/j.mma.20240903.12 AB - In recent years, the double-layered multi-head weighers whose hoppers are arranged in two levels are widely used in the accurate and reliable weighing for packing food products. The weighing processes are mathematically modeled into a single objective optimization problems. The objective of packing problem is to minimize the total weight of combined hoppers for a package under the condition that the total weight must be no less than a specified target weight. This paper proposes a novel single objective optimization approach for double-layered multi-head weighing process. More precisely, relying on a new bound on the optimal weight, this study accurately determines the number of hoppers to be combined at each packing operation, and find the best possible hopper combination using the single-objective algorithm. This method significantly speeds up the packing process as a whole. According to the present approach, the candidate number of hoppers to be combined can be taken one or two integral values. The probability that the accurate number of hoppers to be combined becomes one integral value is explicitly calculated, which is the performance factor to the previous one. In addition, results from the numerical experiments to show the effectiveness of the proposed approach are presented. VL - 9 IS - 3 ER -