New approaches of the optimum design of the linear electromechanic actuators.
Nasui, Vasile ; Cotetiu, Radu ; Cotetiu, Adriana 等
1. INTRODUCTION
The present day process of intense preoccupation for the
improvement of the industrial orders, the achievement of an efficient
pattern for the research of efficiency is essential. The exploitation of
the mechanical technique system has implications on the studies viewing
the factors that determine the efficiency pattern in the primordial sense. Because in the modeling conditions as a rational activity viewing
the way of doing it are only an application of the efficient technical
principles in the given conditions. In the present day context, it is
important that the technical optimum is the optimum of substance
consumption which must be followed in a special way besides other
principles which view systemically and globally the entire
phenomenological process of the mechanical systems (Banica, 2006).
The research has in view the establishment of an optimum solution
according to the destination of the actuator using a great variety of
solutions, starting from the simple recovering mechanisms of the
mechanic, hydro, pneumatic, electric types up to the recovering /
regeneration systems of braking energy. The use of new solutions,
including the informatics technology and the applications of the
proposed research is the answer to the challenges of the society of
knowledge which targets the engineering solutions of controlling the
movement through intelligent and efficient systems (Borangiu, 2003).
The proposed theme has a scientific importance because it
approaches research in a top interdisciplinary domain which targets the
energetic efficiency of mechanic systems and the protection of the
environment. It targets the synthesis and the development of knowledge
in order to generate new solutions of actuators having a structure with
a combination of elements within an assembly, superior quality and on
the basis of new principles using the way of deductive analytical
logistics. The conception research of new types of actuators requires an
interdisciplinary approach and a complex process of interference, of
collaboration and coordination of scientific knowledge in the field of
mechanical, informatics studies (Dumitru & Strajescu, 2004). The
linear actuator consists of a motor turning a screw in which the nut on
screw is not allowed to rotate. The main component parts of an actuator
are represented in figure 1, including: 1-mechanism actuator;
2-controller; 3-electric engines and 4-reducer transmission (fig.1).
2. APPRECIATING THE SOLUTIONS OF PROJECT USING VARIABLE FUNCTIONS
When the value function is established, relevant for an objectively
chosen criterion for optimization, it is relevant to appreciate its
characteristic. The experience shows that the focus should be on finding
appropriate mathematical expressions of appreciation. Choosing this
concept of a solution which fits best the criteria of the list of
requirements offers the perspective of an optimal achievement. With this
purpose, it is necessary to have information on the predictable
behavior, respectively on the characteristics of the product which is to
be developed on the basis of the proposed concept. An appreciation made
on the basis of this information can have as objective either the
comparison with the ideal solution, establishing an optimization degree.
To comprehend more completely the properties of making the product
and the concept we are going to regulate characteristics and to
establish the calculus methods or experimental models. In order to come
up with appropriate models we can make use of the theory of systems. For
the elements of the system we should search modules of model which have
an analogue behavior using analogies and similitude's on which we
research the whole behavior. We proceed to the systematic variation of
system parameters, even getting in this situation to a quantity
optimization regarding certain objectives. After establishing a system
of objectives and of criteria of appreciation, we order the objectives
in a mould, which criteria as objective, which is one step closer to the
ordered representation of information (Maties et al., 2000).
We indicate all the known properties of the electro mechanic linear
actuators, submitted to the analysis, called "measures of
objective" in the technical of the systems, we speak of
"results of objective" which represent an objective indication
on the achievement of the proposed appreciation criteria: energy
consumption, specific power, specific weight, efficiency, subsystems
which define the respective model, for the calculus of the power of
actions, of acceleration, of the precision of positioning, of
vibrations, of dynamic quality of any configuration of linear actuator
submitted to analysis.
The validation of the model is done by interpreting the results and
comparing the behavior of the elaborated model and the real system. We
can improve the model step by step until we obtain a physic and
mathematic model which can fulfill the requirements of the study of the
technical phenomenon.
[FIGURE 1 OMITTED]
These researches allow the experimental solving of some problems
which can't be theoretically worked out, or can be used to validate
or generalize the theoretical models.
3. EXPERIMENTAL RESEARCH
The experimental research on the trial stand aim at determining
functional dynamic parameters such as the absorbed power, the load and
the working speed the efficiency of the type dynamics in order to label
the energy of the product. To check the theoretical considerations we
made the some experiments with actuators equipped with screw-screw
driver mechanism with trapezium spiral and ball screws. The measurement
stand where the experiments were made is presented in figure 2.
In mechanical transmission mechanisms with screw-nut with friction
sliding or rolling of experimental research to extract the following
relationship in determining the efficiency:
[eta] = 1/1 + k x d/p (1)
where:
d is the overage diameter of the screw;
p--the step of the propeller of the screw thread;
k--a dependent coefficient that depends on the constructive type of
the screw, depending on whether the friction namely: k = 0,33 for
sliding; k = 0,033 for rolling. The measurements have been done on a
trial stand in loading registering powers absorbed and then the
efficiencies have been calculated and represented in the graphics in
figure 3.
First of all, it results the importance of the constructive
solution and then the functioning conditions, the working speed and the
oiling conditions. Therefore, the real efficiency can be determined
after the experiment taking into account all these aspects, the geometry
of the screw's profile and the dependency of the friction angle by
several factors. The increase of the actuator's efficiency can be
achieved, in general, by: the reduction of the complexity, by the
incrementing of the efficiency of the components, by the reduction of
the friction losses, appropriate maintenance strategies. In the
optimization of the efficiency two main directions have been developed -
the efficiency maximization by the reduction of the friction and the
minimization of the cost by saving at the maximum.
The radical solution is in general achievable by replacing the
kinematics couple with an appropriate kinematics polycouple having also
rolling elements. As a consequence of the modeling, new kinematics
solutions of linear actuators have been achieved which, by passing the
selection stage, have been optimized and materialized into a range of
constructive typo-dimensions. The research stage led the comprehension
of the structural-phenomenological process and to the establishment of
the physical - mathematical pattern. Finding the optimum technical
solutions was the result of the optimization process for these patterns,
written down as kinematics schemes projects and calculating models
(Nasui, 2006). The results of the research stage contain a new approach
of the optimum design where the classical methodology is developed along
with the aspects of the phenomenological dynamical modeling.
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
4. SUMMARY AND CONCLUSIONS
The solutions presented from the constructive point of view
correlated to the one of the movement control is an important
contribution to the development of the same modern system of linear
acting for a larger range of applications, from the most common ones to
the intelligent systems of flexible fabrication. Their development is
not limited since they are part of the top industry which requires high
levels regarding the generation and the control of linear movement.
Pursuing a systematical tackling of the optimization by completing the
dynamic model, these parameters performing rototranslation systems have
been achieved (Nasui, 2009).
The applicative and experimental researches viewed the practical
checking and the making up of the theoretical patterns used in the
output and also convergences to the ways of approaching the problems to
reality. The work integrates itself into the present day researches in
the field of the development of the modern mechanic transmit ions making
contributions in their optimal design. The work deals with the
assimilation of some modern systems of action of linear electro mechanic
actuator type used to machine tools from intelligent systems of
production.
The development perspectives aim at optimum solutions equipped with
mechanisms of transmission of the movement with high efficiency and
viability. In the future, the researches will continue in order to
realize a structural change on the basis of new physical principles of
acting, leading and controlling the actuators.
5. REFERENCES
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Maties, V., Mandru, D., Tatar, O. & Maties, M. (2000).
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