Research and application of smart home appliance interconnection technology

With the rapid development of intelligent control technology, computers and information technology, the trend of information appliances IA (Information Application), computers and communications integration has become increasingly obvious, and home networks have emerged. Customers have higher and higher requirements for home appliances, and home appliances have become intelligent and networked. That is, home appliances do not need to be controlled by people. People's work is just to set a series of objective functions and target parameters as well as work and rest time, and other work is done by the microcomputer of the home appliance through certain calculation methods and control methods. For example, smart air conditioners can automatically adjust their working state according to different seasons, climates and user locations to achieve the best effect, and try to save energy while meeting people's needs. Most of the electrical equipment in the home can be connected to the network in a certain way, and these devices can be remotely controlled and automatically controlled. Home networking realizes the exchange of internal and external information in the home, and provides people with a variety of personalized, convenient, comfortable, safe and efficient services, so it has a huge potential market. At present, my country's smart home appliances are in the trial stage and need further research and development. The goals of energy saving, consumption reduction, health, environmental protection, and comfort of home appliances can be more easily achieved through the intelligence and networking of home appliances, thereby achieving energy saving in the use process. As a home appliance company, the research and application of energy-saving technology, intelligent technology, and networking technology for home appliances will play an important role in the overall upgrading of China's home appliance industry and maintaining its competitive advantage.
The purpose of this article is to solve the key technologies of home appliance interconnection, thereby improving the level of intelligence and networking of home appliance products in our province, reducing household energy consumption, meeting the requirements of energy saving, environmental protection, comfort, and convenience of home appliances, and enhancing the market competitiveness of home appliance products in our province.

1 Smart home appliance network
Smart home appliances are home appliances that "have feelings, can think, communicate well, and learn". Smart home appliances are home appliances formed after the introduction of microprocessors and computer technology into home appliances. They have the functions of automatically monitoring their own faults, automatically measuring, automatically controlling, automatically adjusting, and communicating with remote control centers. For example, in the hot summer, before leaving get off work, you can send a text message command and the air conditioner at home will start working; when sleeping, the air conditioner can sense the temperature of the owner and automatically adjust the temperature, thus eliminating the worry of catching a cold due to the air conditioner; the washing machine can achieve accurate washing time, accurate water consumption, and accurate drying time, which is efficient and energy-saving. Therefore, energy saving and environmental protection have also become a trend in the development of smart home appliances. The smart home appliance network includes smart home appliance gateways, external networks and local networks, home appliances, security equipment, etc. The key to realizing the interconnection of smart home appliances lies in the development and application of home gateways. In the home information network technology system, the connection between the home and the Internet requires a home network central controller (home gateway). The home gateway is connected to the Internet network externally, and the home appliance interconnection is centrally controlled and managed through the home internal LAN, as shown in Figure 1. As the core device of the smart home appliance network, the home gateway manages or controls the network access of home appliances.

In the future, smart home appliances will develop in three directions: intelligence, self-adaptation and networking. Intelligence is the function of home appliances to simulate the thinking or activities of many kinds of people as much as possible; self-adaptation is the ability of home appliances to automatically adapt to the working mode and process according to their own status and external environment. Therefore, this ability makes home appliances in the most efficient and energy-saving state during their use; networking is a form of building a home appliance society. Networked home appliances can be remotely managed and controlled by users, and home appliances can also be interconnected.

2 Embedded Home Gateway
2.1 Introduction to Embedded Home Gateway
Embedded systems are application-centric, based on computer technology, and their software and hardware can be tailored. They are suitable for special computer systems with strict requirements on functions, reliability, cost, volume, and power consumption of application systems. They are generally used to realize functions such as control, monitoring or management of other devices. The gateway is essentially an IP address that connects a network to other networks. A typical home gateway integrates ADSL access function and LAN side wireless access function, and has the functions of router, hub and modem. In order to realize that each home appliance can exchange information with the outside world, it is necessary to combine the embedded system with the home gateway and design an embedded home gateway to achieve this. It can connect embedded home appliances such as televisions and refrigerators to the Internet through the home gateway and transform them into a home appliance network.
The embedded home gateway is a network device located inside a modern home. Its function is to connect home users to the Internet, enable multiple smart devices in the home to communicate with each other, or enable all these smart devices to connect to Internet services. From a technical point of view, the embedded home gateway implements bridging/routing, protocol conversion, address management and conversion within the home and from the inside to the outside, and assumes the responsibility of a firewall.
2.2 Functions of embedded home gateways
Since the embedded home gateway is a bridge connecting the home network with the external Internet, it plays an important role. The functions that the embedded home gateway can provide will directly affect the use, control and management of smart home appliances. A good embedded home gateway should enable information inside and outside the home to be exchanged safely and efficiently, and should have the following basic functional characteristics:
(1) Sharing information: Through the home gateway, residential users can obtain various home services. For example, receiving e-mails, browsing various online information, and subscribing to various newspapers and periodicals;
(2) Intelligent management: It will manage the operation of communication appliances in the home, so that multiple PCs and other information devices in the home can effectively share broadband access to ensure the normal operation of the home network system;
(3) Automatic operation: It can connect all home appliances in the home to the network. Through relevant management and control software, it can realize the management, monitoring and fault diagnosis of home appliances. If a fault occurs, the home management and control system will have a corresponding prompt and send a signal to the home owner;
(4) Energy saving and safety: Through the network management system, the operation of home appliances can be remotely managed and controlled to improve the efficiency of home appliances; at the same time, various detection and alarm devices can be installed in the home to manage and control home safety, fire protection, etc. For example, if a gas detector is installed at home, when there is a gas leak, when the gas detector detects that the gas concentration reaches the critical point set by the explosion or poisoning alarm, the gas detector will send out an alarm signal to effectively prevent explosions, fires, and poisoning accidents;
(5) Simple operation: Because the network system is used by most users, considering the differences in various aspects of users, the operation of the system should be simple, convenient, and reliable, and most people will use it;
(6) Firewall: Network security has always been an issue that needs to be focused on. The embedded home gateway should have a certain ability to prevent network attacks and provide a relatively safe network environment for the home network. 2.3 Advantages of embedded home gateways
The embedded home gateway is implemented through an embedded operating system, so it also has the characteristics of an embedded system. Therefore, we can configure different embedded home gateways according to different networks. The embedded home gateway not only has the functions of an ordinary home gateway, but also has firewalls and information encryption functions in communication. Firewalls can prevent illegal access and attacks on home devices by external networks; encryption, a more powerful means, can provide confidentiality, authenticity, integrity and restricted access to data.

3 Home appliance interconnection system based on embedded
home gateway The structural framework of the home appliance interconnection technology system based on embedded gateway introduced in this paper is shown in Figure 2. The hardware platform of embedded home gateway is centered on ARM9 microprocessor. It is connected to the Internet through LAN, and the home appliances in the home are connected through the wireless LAN inside the home to realize the management and control of home appliances. In this way, users can query and control the operating status of home appliances through PC, and can also manage and control home appliances locally through handheld control terminals in the home.

The system mainly adopts the direct access topology structure, and the home devices of the device form multiple star networks to realize local and remote real-time control of the home devices. The hardware platform consists of an embedded host gateway, a microprocessor, a wireless communication control module, peripheral devices, HUB, etc. HUB is a multi-port repeater. When the HUB is the central device, a failure in a certain line in the network does not affect the work of other lines. It can provide users with a variety of network access methods, such as dial-up, broadband network, etc. The wireless communication module realizes the connection with multiple network home appliance controllers through serial communication. Since the embedded Linux operating system is an open source, scalable, small-kernel but very stable software platform system that can handle complex tasks, the operating system of the application gateway is intended to use the embedded Linux system.

4 Home appliance network communication control process
(1) Register the home gateway: After the user logs in to the embedded home gateway through the embedded Web server page, the home gateway is registered first.
(2) Sending control information: After successful registration, the home appliance control information is submitted to the home gateway, and the home appliance control information is converted into home appliance control instructions. Then the embedded home gateway application packages the home appliance control instructions according to the communication protocol and sends them to the home appliance through the wireless module.
(3) Receive control instructions and execute: After the home appliance receives the control frame, it unpacks the information frame according to the above protocol frame format, extracts the frame type, valid control instructions and related valid information, and sets and operates the home appliance accordingly.
(4) Sending back the current status information: After the operation is completed, the current status of the home appliance after setting is packaged in the above status frame format according to the above format and sent to the embedded home gateway.
(5) Receive new instructions and execute them, and the communication ends: After the embedded home gateway receives the status frame sent by the home appliance, it sends a confirmation frame to the home appliance, and then calls the corresponding home gateway application for processing according to different status frames. If the embedded home gateway does not receive the status frame within the specified time (300 ms), it will resend the control frame to the home appliance three times. When the home appliance receives the confirmation frame sent by the embedded home gateway, the communication ends.
If the home appliance does not receive the confirmation frame, it will continue to send this status frame three times before ending. If the embedded home gateway does not receive the status frame sent by the home appliance, the embedded home gateway will report the setting failure to the user and end the communication.

5 Conclusion
With the continuous development of information technology and networking, home appliances are evolving in the direction of intelligence, networking, and informatization, constantly satisfying people's pursuit of entertainment, information, comfort, convenience, and freedom. The interconnection and remote control of smart home appliances are the products that adapt to this trend. This system combines embedded technology and networking technology to make the interconnection of smart home appliances more convenient and reliable.