## 2 Process and System Description  
The bonding force between particleboards is obtained by the bonding of adhesives, and the specific surface area of particles is large, so uniform sizing is very important. Particleboard bonding adhesives belong to thermosetting adhesives, which need heating to achieve curing bonding and the curing process is irreversible. Therefore, in the process of sizing, the control system must ensure that there is no overshoot. The system is divided into two parts: glue mixing and glue dosing. The schematic diagram of glue mixing system is shown as Figure 1. The volume of various raw materials, include curing agent, waterproof agent, curing buffer agent, water, and adhesive, is measured by a liquid level detector. The electronic control throttle valve, that controls itself, is set to the proportion for the system in advance. When the required material reaches the expected value, the valve will close itself. Then the raw materials are mixed by gravity flow into the mixing tank. Ball valves are used to control the amount of raw materials required. According to the formula entered into the system in advance, it controls the switch by itself to the amount of raw materials transferred to the glue mixing case, and all the materials are mixed by the agitator in the case. The glue mixing case is divided into two parts, one for the surface layer of the particleboard and the other for the core layer. The sketch of the controlled system is shown in Figure 2. It consists of a particleboard supported device, a glue supported device, and a mixing device. The conveyor chute and the belt weighing device make up the supported device and all particleboards are supported by it. The screw conveyor feeds the particleboard into the discharge chute; the weighing sensor measures the weight of the particleboard; and the rotation speed of the belt weighing device is measured by gyral coder. The glue supported device consists of a glue control pump and a flowmeter, which the E+H type flowmeter is chosen. The glue and particleboard are mixed by a mixing device. During the process of dosing particleboard, the screw conveyor conveys the particleboard to the mixing device and through the screw bin and valve B. The instantaneous weighing signal is gathered by weighing sensor B, which is located on the weighing conveyor belt. When the particleboards are transported, the instantaneous weight of the glue is calculated on the basis of the amount of the glue input. Then, in the light of the relationship between the rotation speed and the output of the pump, we calculate the pump speed. The essential structure of the particleboard mixing and dosing system is shown in Figure 3. Glue flow input signal is the desired value of the controller. The ultimate goal of the control system is to ensure that the output glue flow reaches the desired value. Firstly, we get the glue flow through the flow sensor. The sensor is an E+H flowmeter as shown in Figure 2. It measures the output glue flow velocity in the pipe and the input value is compared with it and the obtained error is sent to the controller. For minimizing the error, the controller continuously linkers with the frequency of the converter and, through it, the speed of the squirrel-cage motor is changed and it will result in the change of the output glue flow. By doing this, the controlled glue supplying pump can be stable. Figure 1: Schematic diagram of glue mixing system. (1. Curing agent; 2. Waterproof agent; 3. Curing buffer agent; 4. Water; 5. Liquid level detector; 6. Quantitative barrel; 7. Electronic control throttle valve; 8. Feeding tube; 9. Cylinder; 10. Ball valve; 11. Blanking tube; 12. Agitator; 13. Glue mixing case). Figure 2: Particleboard glue mixing and dosing system. Under low frequency (15 HZ input frequency) conditions during particleboard dosing and mixing, the controlled system becomes a time-delay system due to the hysteresis and inertia of the motor and pump. A time-delayed object can be formalized as a transfer function mathematical model as follows.