| Concrete pump truck is a kind of engineering machinery with the integration of transporting and casting concrete. Considering its convenience, high efficiency and safety, it has been widely used in the construction of high-rise buildings, high-speed rails, bridges, etc. With the increasing demand for its performance and considering the development trend of the industry, the future trends of concrete pump truck are intelligent boom, boom vibration reduction technology, automatic reverse technology, energy-saving technology, as well as improving the pumping capacity and realize the vehicle condition monitoring and fault diagnosis, etc.The pumping system adopts double cylinder driving mode with electric or hydraulic pilot switch valve reversing, pumping pulsation cause the forced vibration of boom and bring structure fatigue damage. At the same time, it will impact construction efficiency and precision.This topic first studied the key technology of pump truck pumping hydraulic system. The current widely used open circuit hydraulic system is analyzed on how to reduce the hydraulic shock of the direction valve reversing in the pumping process, such as improving hydraulic component structure, the using of accumulator, choosing suitable directional valve transition function, optimizing the control performance of the whole system, etc.; Closed loop hydraulic system has smaller hydraulic shock in comparison with open circuit hydraulic system. However we must solve the key problems in the application process, including quickening the response of the closed type pump reversing, "SN" control to prevent pressure shock, constant power control, multi-function pressure and flow control, etc.Another important task of this topic is to suppress the boom end vibration under a fixed posture during pumping process. First we analyzes the vibration mechanism of the boom in the process of pumping concrete, including the car body vibration caused by pumping system, the concrete pulsating flow in pipelines and the friction load in the boom end, large movement sparking the first order natural frequency of the boom, pumping hydraulic system vibration impact and other interference, etc. These factors causing the vibration of the boom can be equivalent to interference effects on boom. On this basis, this topic put forward the feedforward control strategy based on boom interference force estimation. Based on the independent modal space control method, we establish the boom disturbance estimator to estimate all external disturbance force on the boom, and then eliminate the causes of its effects on boom vibration through an opposite control action. It belongs to active control category.Finally, we set up the simulation model for the closed loop hydraulic system, studied the influence of the existence of the damping hole on the response characteristics of the pump and the system stability. Furthermore, we carried on active vibration control experiments in terms of the boom horizontal posture and upright posture when pumping concrete, the boom vibration amplitude is weakened to about 35% and 40% respectively, verified the correctness of the analysis of the boom vibration mechanism and the effectiveness of the proposed control strategy. |
