The control of the inlet and outlet of the traditional directional control valve is carried out through a valve core. The corresponding relationship between the two ports listening to the opening has been determined as early as when the valve core is designed and processed, and it is impossible to modify during use, so that the flow through the two ports Or pressure can not be controlled independently of each other. With the decrease of the cost of microprocessor controller and sensor components, the continuous improvement of control technology has made double-spool control technology available in the field of construction machinery. Utronics, UK, has developed its double spool valve with its own technology and patent advantages and has been widely used in such excavators, trucks, loaders and backhoe loaders as JCB, Deere, DAWOO and CASE. . To meet China's construction machinery products on the hydraulic system functional requirements. Stability and automation of the continuous improvement of the level of Utronics products to enter the Chinese market at the right time, is now initially completed Xiaogang (5t) loader, Zhanyang (8t) excavator prototype debugging and entered the pilot phase. 1, the traditional single-spool valve defects Traditional single spool valve hydraulic system composed of a reasonable solution to the following conflicts between the function and control: (1) the hydraulic system designed to improve system stability , Reduce the impact of load changes on speed, or sacrifice some of the features we want to achieve, or add additional hydraulic components, such as speed control valve, pressure control valve, etc., by increasing the damping, increase system speed stiffness to improve system stability. However, such components will reduce the efficiency of the increase, a waste of energy; will also make the whole system of lower reliability, increase costs. (2) Due to the particularity of the commutation structure, users must purchase the corresponding hydraulic components when realizing a certain function. In addition, the construction machinery manufacturers design corresponding functions according to different end user requirements, which will cause the manufacturers to purchase Similar, multi-standard hydraulic control components to meet the needs of different functional requirements, is not conducive to product genericization and product management, will greatly increase product costs. (3) Since the actuator enters and exits the hydraulic fluid through a valve spool for control, it is not possible to control the pressure on either side of the actuator separately. Therefore, the back pressure on the oil side acts on the opposite direction of the actuator movement. As the back pressure on the oil side increases, the pressure on the oil inlet side must be raised for the movement of the durability actuator. This will make the hydraulic system to increase the function of consumption, low efficiency, increased heat. Hydraulic system with double spool technology, because the implementing agencies into and out of the oil side of the valve spool position and control methods are independent of each other, so that through the two different combinations of spool control, the use of software programming can be very good to solve the traditional Single-valve system can not solve the problem, but also can easily achieve the traditional hydraulic system difficult to achieve the function. 2, two-valve spool valve two basic control strategies As the two-spool valve port for the flexibility to control the two ports, respectively, to take flow control, pressure control or flow pressure control. Positive introduction of two simple control strategies. (1) The load direction remains unchanged throughout the work We know that for the truck crane, excavator, loader and so on, the hydraulic cylinder in the entire work load direction has remained unchanged. The following crane luffing hydraulic cylinder as an example to explore the double spool control strategy. Crane luffing cylinder in the course of its work force, the load direction is always the same, so we can take a hydraulic cylinder with rod pressure control, rodless chamber with flow control control strategy. Rodless chamber flow control is connected to the rodless chamber side of the valve by the pressure on both sides of the front and back, and then according to the required flow into or out of how much to calculate the size of the valve opening; rod chamber side pressure control so that the Side to maintain a low pressure, making more energy efficient. Because we use flow control in the rodless chamber, the balance valve used in the original control system can be replaced by a pilot operated check valve. This eliminates the system instability caused by the balance valve, thereby improving system stability. (2) The direction of load changes during working In this case, "inlet side pressure control and outlet side flow rate control" are adopted, pressure is controlled at the rod chamber side of the hydraulic cylinder, and flow control at the rodless chamber side . If the load direction is unchanged, because of the flow control of the oil side, we can replace the two-way balance valve with the pilot operated check valve to improve the stability of the system. The pressure side of the inflow side is used to maintain a lower reference pressure, on the one hand to increase the system efficiency and on the other hand to keep the system from cavitation. In order to make the load change direction of the working mechanism can be well controlled, another PI controller will be applied to the rod cavity pressure controller, when the load direction changes, rodless cavity pressure will be reduced; if you still Rod chamber to maintain a very low pressure, when the load is large, the hydraulic cylinder will move in the opposite direction. In this case, we can monitor the rodless chamber pressure with the added PI controller. When the PI controller detects that the rodless chamber pressure is lower than the set reference value, it will increase the pressure set by the rod chamber pressure controller Pressure, thus ensuring the normal operation of the system. 3, Ultronics hydraulic control system Ultronics company is a design, research and manufacture of electronic hydraulic technology company. The hydraulic control system uses CAN bus communication, dual spool control technology, the combination of two spool control, the actuator can achieve a variety of control to improve system stability and reduce energy consumption, but also allows the system Simpler, lower costs, speed up product development, these are the traditional electronic systems can not do. Ultronics control system hardware generally by the joystick, electronic control unit ECU, regulating valve, double valve spool valve and external sensors or switches and other components, during communication through the CAN bus, hydraulic valve manifold for the intersection of electronic control system and hydraulic system Point, another important part of the system is the software. The handle is optoelectronic non-contact form, with up to 4 proportional output or 2 proportional output and up to 5 switches. Switch is proportional and self-locking options. Its degree of protection reached IP67. The delay characteristics of the handle, the output curve and dead zone can be modified by the special software JoyVal. Electronic control unit ECU for its voltage 12V and 24V two kinds of 25 and 50 Road two interfaces to provide analog and digital input and output interfaces, while the electronic control unit also provides a CAN letter interface, making the system can receive the sensor or Control signal or connect with other system. The ECU stores all the applications needed for system control. The application converts other devices and signals (such as sensor detection signals, engine control system information, etc.) from the handle or connected to the ECU into processed Valve action instructions. The key to the Ultronics control system is its unique double-spool control technology with two spools per valve, which translates into a three-position, four-way valve into a combination of two three-position, three-way valves with both spools both Can be controlled separately, but also according to the control logic of the paired control, and two working oil ports have pressure sensors, each spool has a position sensor, closed-loop control of the sensor signal can be two hydraulic oil Pressure or flow control, with high control accuracy, through a variety of combinations can be a lot of control programs to meet the needs of the system. Each valve has two complete set of mixed-signal ASICs (analog ASICs) and one RISC (reduced instruction processor). These controllers provide excitation and compensation to the sensors, power the control gear, spool control software and CAN bus communication. Valve spool control strategy and the specific parameters can be set or modified by the user according to the requirements of the controlled actuator. When the control valve receives the command, the embedded processor runs the valve core operation control software to realize the set function. The function coordination among multiple valves is completed by the ECU to realize complicated system functions. This hierarchical control makes the application of the system very flexible and easy to build a complex control system. The versatility of the Ultronics control system's functionality is achieved through application software that is tailored to the control software. The features that the Ultronics control system can achieve are extremely broad. Crawler excavators, wheel excavators, loaders and other advanced models in the operating comfort, operating efficiency, operating cost, troubleshooting, environmental protection and other efforts, such as the engine state and hydraulic system adaptive control, specific Job function, etc., using Ultronics system can be achieved. In summary, Ultronics electronic hydraulic control systems enable engineering machinery control systems to be versatile in function, flexible in implementation, via CAN bus communication, unique dual-spool construction and pressure, displacement sensor applications, and closed-loop control of pressure or flow Sex, low cost and control concepts, maintenance mode and many more will lead to a revolutionary change.
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