3D visual management based on BIM smart community spatial positioning

1.
3D visual management of smart community
Compared with the previous threedimensional visualization of BIM technology, the information of each component is more intuitively expressed by lines. Moreover, the threedimensional model of BIM is generated automatically by the information contained in the components, and the components are interactive and feedback. BIM technology can make the community building information accurate to the component level and can show the whole community environment with threedimensional model, which makes the data more accurately express the reality. This is BIM software compared with twodimensional drawings, CAD. The software has its unique advantages, which is very helpful for us to locate the danger source and the people in need of rescue in case of emergency [6].

2.
Information diversification
BIM model contains the detailed information of the building. When the component is created, all the physical information, chemical information, and purchase information of the component will be generated at the same time, and the material schedule can be extracted at any time, including the schedule of structural columns, walls, beams, plates, etc., and including the specific properties of material strength and consumption.

3.
Simulation
BIM technology in community operation and maintenance management can be based on 4D (3D + time) sunshine analysis, acoustic environment simulation, collision inspection, personnel emergency evacuation simulation, energy saving analysis, etc.; based on 5D (3D + time + cost) construction dynamic cost simulation. For example, BIM can be used for collision inspection and virtual rehearsal of construction scheme of equipment and pipeline to be installed during decoration and pipeline equipment maintenance, which can reduce the accident rate and change during construction; BIM can be used for demonstration of residents' safe evacuation, which can not only reduce the manpower and financial resources of evacuation exercise, but also reduce the occurrence of accidents in case of emergency.
BIM software can also simulate the construction progress, import the established BIM model and the project construction organization plan into the Autodesk NavisWorks software timeliner to simulate the construction organization, simulate the construction process in advance, and find the work conflict and idle time in the construction organization plan, which is helpful to save the construction period and reduce the construction cost [7].

4.
Support multiple data transmission formats for information integration and sharing
BIM software implements the international IFC Standard industry foundation claim. The Revit series software of Autodesk company supports CAD graphics format (DWG \ DXF \ DGN \ SAT), FBX format, gbxml format, ODBC database format (open database activation), Excel, video recording and animation format, etc.; in addition, Revit also provides API secondary development interface, and users can use C + according to their own needs for the project VB. NET Language and so on.
Special needs of the elderly for the community environment

1.
Physiological characteristics of the elderly

1.
Physical motor function
Although the physical function of the elderly aged 65–75 years gradually declines, they can basically take care of themselves. Once they are 75 years old, there will be certain obstacles in their activities, and they need to use crutches, wheelchairs, and other tools. After 85 years old, the elderly's physical function will accelerate decline, and they need continuous care.

2.
Perception and nervous system
The vision of the elderly is decreased, the ability of color recognition is gradually reduced, the visual field is narrowed, and cataract is easy to occur; in terms of hearing, the elderly can reach 65 years. After the age of 65 years, the hearing is relatively weak, sometimes it needs to borrow hearing aids, and it is easy to be interfered by noisy sounds; it is relatively slow to distinguish things with touch, taste, and smell, mainly manifested in: the elderly are not sensitive to the peculiar smell in the air and slow to perceive the temperature and humidity. The decline of the nervous system in the elderly makes the elderly have poor memory, slow response, and poor ability to accept new things. This makes it easy for the elderly to get lost, walk away, or have accidents [8].

2.
Psychological characteristics of the elderly

1.
Psychological changes brought about by changes in family roles
Once the old man retires, he will feel empty and lonely when he changes from the dominant position of the head of the family to the role that needs to be supported by his children. With the increase of his age, his spouse or relatives will gradually die, which makes the old man feel more lonely and fear of death. With the increase of his age, he will gradually have no economic source, and it is difficult to accept the role of supporting his children. We will be sensitive to money.

2.
Psychological changes brought about by changes in social roles
After retirement, many old people gradually become leisurely from a busy and regular life, which makes a lot of free time for the old people unable to have fun. The old people are easy to feel lonely, lost, and abandoned, which is extremely harmful to the physical and mental health of the old people. Many scholars believe that the real aging of the old people starts from the separation of social responsibility. In terms of interpersonal relationship, the old people leave their work team and environment, which makes the old people need to establish new interpersonal relationship in order not to be divorced from the society.

3.
Psychological changes brought about by physiological changes
The elderly's physical function is gradually declining, and there are certain obstacles in their activities. They need to use crutches, wheelchairs, and other tools to reduce their eyesight, which makes their range of activities smaller. In addition, their perception ability is weaker, and their hearing loss makes them reluctant to communicate with others, and they become blocked with information, emotional instability, and depression, which makes them gradually isolated from society, and their physiological functions. The changes brought to the mind in turn aggravate the aging of the elderly. With the growth of age, the memory and reaction ability of the elderly gradually decline. In order to avoid loss and accidents, it will also lead to that the elderly are not willing to go out and walk, the elderly lack of exercise, and the physical function will gradually decline.

3.
The special needs of the elderly for the community environment
The physical and psychological characteristics of the elderly determine their way of life and mentality. When carrying out the elderly care management in the smart community, we should fully consider the elderly's needs for safety, environment, accessibility facilities, daily life, communication, selfrealization, and constant attention, so as to ensure the normal, safe and healthy operation of the elderly's daily life and enrich their spiritual life, there are different solutions according to the different service needs of the elderly [9].
The physical and psychological characteristics of the elderly are shown in Fig. 1:
The weight calculation of the entropy weight method of the smart pension space positioning structure
The structural entropy weight method should go through three steps: expert scoring, blindness analysis, and normalization.

1.
Expert scoring
Select a certain number of experts and apply the expert scoring method to sort the factors in a typical way.

2.
Blindness analysis
After the standard classification of factors, some experts may be classified. Therefore, the deviation of expert ratings should be further elaborated. The entropy weight method should be used [10].
There are k experts for scoring, including n influencing factors, and the typical ranking matrix obtained is \(X_{{kn}}\), \(x_{{ij}}\) is the evaluation of the factor j by the expert i, \(x_{{ij}}\) takes any natural number from 1 to n, that is, \(1 \le x_{{ij}} \le n\), and \(x_{{ij}}\) is a natural number.
The membership function that transforms the typical ranking is:
$$y(x_{{ij}} ) =  \lambda pn(x_{{ij}} )\ln (x_{{ij}} ).$$
(4)
Let \(pn(x_{{ij}} ) = \frac{{m  x_{{ij}} }}{{m  1}},\lambda = \frac{1}{{\ln (m  1)}}\), then:
$$y(x_{{ij}} ) =  \frac{1}{{\ln (m  1)}}\left( {\frac{{m  x_{{ij}} }}{{m  1}}} \right)\ln \left( {\frac{{m  x_{{ij}} }}{{m  1}}} \right).$$
(5)
Let \(v(x_{{ij}} ) = \frac{{\ln (m  x_{{ij}} )}}{{\ln (m  1)}}\), then:
$$v(x_{{ij}} ) = \frac{{\ln (m  x_{{ij}} )}}{{\ln (m  1)}} = 1  \frac{{y(x_{{ij}} )}}{{\frac{{m  x_{{ij}} }}{{m  1}}}},\quad i \le k,j \le n.$$
(6)
Set the membership matrix to D, where \(d_{{ij}}\) is equal to \(v(x_{{ij}} )\). Assuming that k experts have the same importance on the index \(v_{j}\), the average recognition degree of \(v_{j}\) is:
$$d_{{ij}} = (d_{{1j}} + d_{{2j}} + d_{{3j}} + \cdots + d_{{nj}} )/k.$$
(7)
Expert uncertainty about \(v_{j}\) caused by cognition is called "cognitive blindness" and is denoted as \(R_{J}\), then:
$$R_{j} = [(\max (d_{{1j}} ,d_{{2j}} , \ldots ,d_{{kj}} ) + \min (d_{{1j}} ,d_{{2j}} , \ldots ,d_{{kj}} ))]/2.$$
(8)
Make:
$$w_{j} = z_{j} /\sum\limits_{{j = 1}}^{n} {z_{j} }.$$
(9)
Then, \(W = \{ w_{1} ,w_{2} , \ldots ,w_{j} \}\) is the weight set of index set \(U = \{ u_{1} ,u_{2} , \ldots ,u_{j} \}.\)_{.}
The quality evaluation of smart pension space is based on TOPSIS method
TOPSIS [11] is a multiattribute decisionmaking method. The principle of the method is to: first analyze the weight of each influencing factor, collect data for the influencing factor, form an initialization matrix for each plan, and standardize the initial matrix and then determine an ideal point. The scheme closest to the ideal point is the best scheme. This article uses TOPSIS to evaluate the impact of BIM smart community pension quality and analyzes the impact of BIM on smart community pension quality. The specific implementation steps of TOPSIS method are as follows:

1.
Establish an initialization matrix Y, \(y_{i}\) is the influence value of the evaluation j factor of the item i, i = 1, 2, 3,…, m, j = 1, 2, 3,…, n m projects, n influencing factors.

2.
Normalization of matrix standards.
Normalize the initial matrix Y according to the following formula to obtain the matrix \(Y'\), \(Y' = (y'_{{ij}} )_{{mn}}\), as follows:
$$y'_{{ij}} = \frac{{y_{{ij}} }}{{\sqrt {\sum\limits_{{i = 1}}^{m} {y^{2} _{{ij}} } } }},\quad i = 1,2,3, \ldots ,m,\quad j = 1,2,3, \ldots ,n.$$
(10)

3.
Determine the ideal point
The key to TOPSIS is to find scientific and reasonable ideal points [12], where ideal points are divided into positive ideal points and negative ideal points. The methods for determining positive ideal points and negative ideal points are as follows [13]:
Get the ideal point vector: Positive ideal point vector is \(\lambda ^{ + } = (\lambda _{1} ^{ + } ,\lambda _{2} ^{ + } , \ldots ,\lambda _{n} ^{ + } )\).
Negative ideal point vector is \(\lambda ^{  } = (\lambda _{1} ^{  } ,\lambda _{2} ^{  } , \ldots ,\lambda _{n} ^{  } )\).

4.
Calculate the distance from each item to the ideal point [14]
Distance to positive ideal point:
$$M_{i} ^{ + } = \sqrt {\sum\limits_{{j = 1}}^{n} {u_{j} (y^{'} _{{ij}}  \lambda _{j} ^{ + } )^{2} } } ^{{}} ,\quad i = 1,2,3, \ldots ,m,\quad j = 1,2,3, \ldots ,n.$$
(11)
Distance to negative ideal point:
$$M_{i} ^{  } = \sqrt {\sum\limits_{{j = 1}}^{n} {u_{j} (y^{'} _{{ij}}  \lambda _{j} ^{  } )^{2} } } ^{{}} ,\quad i = 1,2,3, \ldots ,m,\quad j = 1,2,3, \ldots ,n.$$
(12)
Among them, the vector u is the proportion of various factors [15].

4.
Calculate the relative closeness
$$C_{i} = \frac{{M_{i} ^{  } }}{{M_{i} ^{ + } + M_{i} ^{  } }},i = 1,2,3, \ldots ,m.$$
(13)
RFID spatial positioning method of intelligent pension RFID system
RFID has been widely used in finance, logistics, transportation, environmental protection, urban management, and many other industries. This paper uses RFID to identify the spatial location. RFID technology needs to activate the system tag to open the positioning function. In the tag communication protocol module, only [16]
$$V_{{md}} \ge V_{{{\text{active}}}}.$$
(14)
That is, the induced voltage \(V_{{md}}\) provided by the reader should be large enough to be greater than or equal to the activation voltage of the tag chip before the tag can work. The propagation loss of RFID RF microwave in free space is as follows:
$$\begin{aligned} L_{{bf}} & = 201\,{\text{g}}\left( {\frac{{4\pi d}}{\lambda }} \right)\,{\text{dB}} \\ {\text{Or}}\,L_{{bf}} & = 32.45 + 201gf\left( {{\text{MHz}}} \right) + 201gd\left( {{\text{Km}}} \right)\,{\text{dB}}. \\ \end{aligned}$$
(15)
Among them, D is the propagation distance of radio wave, f is the working frequency, and \(\lambda\) is the working wavelength.
The relationship between frequency wavelength and light speed is as follows:
According to the electromagnetic induction theorem, the induced voltage of the label is as follows:
$$V_{{md}} = 2\pi fQNA\mu _{0} H$$
(17)
where q is the quality factor of the tag circuit, n is the number of tag coil turns, a is the tag coil area, h is the magnetic field strength, and F is the carrier frequency. Therefore, the induced electric field that can activate the tag can be obtained [17]
$$H = V_{{imd}} /\left( {2\pi fQNA\mu _{0} } \right) \ge V_{{{\text{active}}}} /\left( {2\pi fQNA\mu _{0} } \right).$$
(18)
Then, there is a minimum label to activate the induced electric field as follows:
$$H_{{\min }} = V_{{{\text{active}}}} /\left( {2\pi fQNA\mu _{0} } \right).$$
(19)
According to the restriction conditions of international organizations on the transmitting power of RFID system, we can choose f = 13.56 MHz, Hmin = 9 dB μ a, and DM = 10 m, so we can get the maximum reader magnetic coupling torque
$$m_{{{\text{RLim}}}} = 4\pi \frac{{\lambda ^{2} d_{m}^{3} }}{{\sqrt {\lambda ^{4}  \lambda ^{2} d_{m}^{2} + d_{m}^{4} } }}.$$
(20)
Among them, \(\lambda\) is the carrier wavelength.
The maximum emission current of RFID system reader can be obtained as follows:
$$I_{{{\text{RMax}}}} = \frac{{m_{{{\text{RLim}}}} }}{{N_{R} ab}}$$
(21)
where N_{R} is the number of turns of reader antenna coil and a and B are the sizes of reading antenna coil, i.e., length and width.
Under ideal conditions, the formula for RFID tag activation is as follows:
$$H = I_{R} \frac{{2ab}}{{\pi \sqrt {4d^{2} + a^{2} + b^{2} } }}\left( {\frac{1}{{4d^{2} + a^{2} }} + \frac{1}{{4d^{2} + b^{2} }}} \right).$$
(22)
At this point, the magnetic field strength of the reader and tag is equal [18].