A new electro-hydraulic braking system for the hot

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The new electro-hydraulic braking system of Wheeled Construction machinery is one of the important components of wheeled vehicles and an important guarantee for driving safety. Therefore, wheeled vehicles constantly put forward newer and higher requirements for the braking system from structure to performance. The traditional braking system has long braking pipeline, many types of valves and complex structure. Especially for vehicles with long wheelbase or trailers, the braking transmission route is long, which often leads to braking hysteresis such as slow response, reduced safety and high cost of the braking system. In recent years, many new technologies and structures have appeared in vehicle braking systems abroad. Among them, wire controlled braking is a new type of braking after vehicle anti lock braking system ABS, traction control braking system ASR and other technologies. The concept of control by wire originates from aircraft manufacturing. With the wide application of electronic technology, this concept has been introduced into the field of vehicle manufacturing, and the applications of technologies such as steering by wire, driving by wire and moving by wire have appeared in vehicles. Different from the traditional braking system, brake by wire replaces some mechanical components with electronic components, becoming an electromechanical braking system. Designing the corresponding program in the electronic control system and manipulating the electronic control components to control the size and distribution of braking force can fully realize the functions of ABS and ASR that can be achieved by using traditional control components

1 classification and characteristics of wire controlled braking system

at present, wire controlled braking system is divided into two types: one is electro-hydraulic braking system (EHB), and the other is electro-mechanical braking system (EMB). The electro-hydraulic braking system is a combination of electronic and hydraulic systems. The electronic system provides control and the hydraulic system provides power; The electric wire and electric brake are used in the electromechanical braking system to completely replace the force transmission medium such as air or brake fluid and the traditional brake in the traditional braking system, which is the development direction of the braking control system in the future. The common feature of the line control system is that it has electronic pedals whose pedal angle and pedal force can be adjusted and controlled in proportion; It has a program control unit that controls the braking torque corresponding to the pedal angle; The program control unit can realize active braking and other functions based on the input signals of other sensors or controllers

unlike electro-mechanical braking, electro-hydraulic braking will not occupy the space near the wheel brake and will not add additional weight. Compared with the high energy consumption of 42V power supply of electronic mechanical braking, electrohydraulic braking can fully meet the requirements by using the original vehicle power supply. In order to meet the relative clearance mode of braking of large tonnage vehicles or construction machinery: only the hydraulic system can produce sufficient braking torque. In addition, due to the needs of work and steering, wheeled construction machinery generally has a multi-channel hydraulic system, so it is easier to use the original vehicle hydraulic source to establish electro-hydraulic braking. Therefore, the first step to realize line control in Wheeled Construction machinery is to realize electro-hydraulic braking

2 Wheeled Construction Machinery electro-hydraulic braking system

power braking system is widely used in wheeled vehicles at home and abroad for its superior braking performance and reliability. At present, all kinds of Wheeled Construction machinery imported from abroad adopt full hydraulic power braking system. Although full hydraulic power braking has many advantages over pneumatic hydraulic braking, it still needs a long braking pipeline for vehicles that need remote control, such as self-propelled climbing trucks and container trucks. The electro-hydraulic braking system with the combination of electronic and hydraulic system can not only solve the above problems, but also has more advantages than the conventional full hydraulic power system

the basic structure and principle of the electro-hydraulic braking system of Wheeled Construction machinery is different from that of automobiles. It is realized by adopting new electro-hydraulic technology on the basis of the full power braking system. Figure 1 shows the scheme of wire controlled electro-hydraulic braking system for wheeled vehicles of mico company. The new system adds electronic pedal, electronic control unit, valve driver and electro-hydraulic brake valve, cancels the original pressure control valve, and retains the pump, accumulator charging valve, accumulator and brake in the original full power braking system

its basic principle is: electronic pedal 1 converts the pedal angle into an electronic signal, which is input to electronic control unit 2 and valve driver 3 at the same time. The electronic control unit 2 inputs the control current and signal to the electrohydraulic brake valve 4 and the valve driver 3 respectively. The valve driver 3 generates a control current according to the larger value of the two input signals and inputs it to the electrohydraulic brake valve 5. Electrohydraulic brake valves 4 and 5 "goodbye side 1" series adjust the pressure output to the brake according to the input current

as shown in Figure 1, although the conversion seems complex and increases the number of components, designers can adjust the layout of components and use programmable electronic control unit to realize the functions that the full power braking system of the system cannot achieve

with the electro-hydraulic braking system, the brake valve and hydraulic pipeline can be arranged far away from the cab and closer to the brake. It not only improves the system performance and the working environment of operators, but also reduces the consumption of pipelines and makes the layout of pipelines easier; Using the electro-hydraulic braking system can easily carry out remote operation or increase the remote control operation system without the need of 4. Microcomputer controlled transmission system of material testing machine: at present, some transmission systems of testing machines in the market adopt reducer and adopt more pipelines and valves; The electro-hydraulic system can timely monitor the condition of the braking system, which makes the fault diagnosis and troubleshooting easier and improves the safety of the machinery; The braking signal can also be shared with the engine electronic controller and transmission controller to improve the performance of the vehicle; By adjusting the control scheme, a multi-purpose and multi form braking system can be formed

the electro-hydraulic braking system can realize a variety of control schemes, such as anti lock braking, remote control braking and traction control braking. Figure 2 shows the scheme of mi-co's Electro-hydraulic braking system with traction control. Based on the full hydraulic braking system, the system adds sensors, electro-hydraulic brake valves and electronic control units. A single valve is added to the electrohydraulic brake valve to make the output pressure of the duplex brake valve higher than the pressure generated by the electrohydraulic brake valve and the traction control system. Under normal conditions, the electro-hydraulic brake valve 2 is opened, and the brake pressure is controlled by the brake valve 3, which is proportional to the operation history on the pedal. The speed sensor 1 installed at the wheel edge inputs the generated electronic pulse signal to the electronic control unit 4. When the wheel rotates too fast, according to the control rules, the electronic control unit controls the current sent to each electrohydraulic brake valve, which adjusts the brake pressure from the accumulator. Stop the excessive rotation of the wheels to improve the traction of the vehicle. In the case of poor ground traction conditions, the full power braking system with traction control can help operators ensure that the vehicle has sufficient traction

at present, the implementation of electro-hydraulic braking system still faces some problems, such as control system failure treatment and anti-interference treatment. The electro-hydraulic braking control system needs a monitoring system to ensure braking safety. No matter which electronic control element fails, it should immediately send a warning message. There are various interference signals in the working process of Wheeled Construction machinery, and a good anti-interference control system is needed to eliminate the influence caused by these interference signals. If such problems are not solved well, the system structure will be complex and the cost will increase

3 conclusion

for Wheeled Construction machinery, the development trend of braking system is from pneumatic hydraulic braking to full power hydraulic braking and then to line controlled braking. Using electro-hydraulic braking in braking by wire is the first step to realize the electronization of braking system. Although facing some problems that need to be solved, the multi-functional and multi-form electro-hydraulic braking system formed by the combination of electronic and hydraulic systems can provide more perfect services for equipment operators, and has a wide application prospect. (end)

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