Homem et al. [7] applied the cut-set algorithm to
generate the assembly sequence. It can be assumed as a
traditional geometric feasibility method. The method was
based on the principle that disassembly sequence was the
inverse of the assembly sequence. There were two main
steps in this method: firstly, a liaison graph was built
according to the assembly model of products, and then a
cut-set algorithm was used to conduct an extensive search
to generate disassembly and/or graph that contained all
feasible disassembly sequences. The assembly sequence
can be obtai ned by inversing the disassembly sequence.
Based on traditional geometric feasibility reasoning ap-
proach, Su [8] proposed a systematical approach called
geometric constraint analysis, which uses the constraint
direction and the minimal constraint assembly state to
reason the assembly precedence and get the optimal
assembly sequence. Dong et al. [ 9 ] proposed a method
based on the geometry reasoning with the knowledge of the
directed-connectors after analyzing the characteristics of
directed-connectors, and presented a uniform representation
of parts. According to their research, the approac h could
reduce the computation complexity drastically and the
obtained assembly sequences were more feasible and
practical.
The knowledge-based approach applied the knowledge
of the existing assembly sequence and the past experi-
ence. The knowledge w as usually the assembly sequence
of the typical products in practice. Based on the concept
of the connector proposed by Tseng et al. [10]in1999,
Yin et al. [11]proposedanapproachtofindfeasibleand
practical plans for mechanical assemblies based on a
connector-based structure (CBS) hierarchy, which is a
knowledge-based approach. They proposed an efficient
representation of assembly inform ation to support the
identification of CBSs a nd presented algorithms to bui ld
a CBS hierarchy for an assembly from its connector-
based relat ional mod el auto matically. It is based on the
idea of reusing the existing plan and modifying the
existing plan and geometric reasoning. Dong et al. [12 ]
proposed a collaborative approach to ASP, which is also a
knowledge-based approach. They applied a role-based
model to compress or simplify the product and assigned
the different planning tasks to different designers who
carried out the collaborative planning respectively. Dong
et al. [13] proposed the conn ection-semantics-based
assembly tree (CSBAT) that provi des an appropria te
waytoconsiderbothgeometric information and non-
geometric knowledge. The ways to construct plans for
CSBAT were presented by retrieving the typical base, by
retrieving the standard base or by geometric reasoning.
Zha et al. [14] presented a n ew methodology to generate
all f easible as sembly seque nces of the pro duct by
reasoning and decomposing the feasible subassemblies,
and representing them by using the assembly Petri net
modeling.
In recent years, a lot of researchers began to use heuristic
algorithm to solve the ASP. Zhou et al. [ 15] used a genetic
algorithm to solve the assembly sequence planning prob-
lem. When initializing the population, the expert knowl-
edge was used to improve the composition of population by
inputting the feasible assemble sequence. Guan et al. [16]
used a gene-group-based evolution approach to optimize
assembly processes rather than merely assembly sequences.
A compound c hromosome encode was constructed to
represent th e ab undant assembly process info rmation.
Several specific genetic operators were used to generate
offspring individuals, and an integrated interference matrix
was built to determine whether an assembly process was
feasible geometrically. Li et al. [17] combined the strength
of the GAs and tabu search and proposed a tabu-enhanced
genetic algorithm to optimize the assembly sequence, while
the tabu search is used as local search. Chen et al. [18]
developed a three-stage integrated approach for assembly
sequence planning by using neural networks. In the first
stage, Above Graph and transforming rule were used to
create a correct explosion graph of the assembly models. In
the second stage, a three-level relational model with
geometric constraints and assembly precedence diagrams
were generated to create a compl ete relational model graph
and an incidence matrix. In the third stage, the back-
propagation neural network was employed to optimize the
available assembly sequence. Zhou et al. [19] applied a
modified genetic simulated annealing algorithm to optimize
the assembly sequence. Wang et al. [20] applied a novel ant
colony algorithm to solve the assembly sequence problem.
The local pheromone updating rule and the global phero-
mone updating rule were introduc ed. T he f irst rule
encouraged the exploration of alternatives and the second
rule encouraged the exploitation of the most promising
solutions. It generated the disassembly completed graph
dynamically and implicitly during the search process of the
ants, the assembly sequence was obtained by reversing the
search path of the ants. Several other heuristic algorithms,
such as artificial immune systems [21] and particle swarm
optimization algorithm [22], also have been used to solve
the assembly sequence planning problem.
The advantages and disadvantages of the above three
kinds of method for ASP are listed in Table 1.
In this paper, a memetic algor ithm is used to solve the
assembly sequence planning problem. Memetic algorithm
(MA), firstly proposed by Moscato [23], is a kind of
stochastic global search heuristics in which evolutionary
algorithms-based ap proaches are combined with local
search techniques to improve the quality of the solutions
created by evolution. Compared with GA, MA is able to
make a better exploration of the neighborhood. MA has
1176 Int J Adv Manuf Technol (2010) 49:1175–1184