# Accurate Modeling, Operation Laws and Commutation Timing Matching for Concrete Pumping Systems
## 1 Introduction  
The concrete pumping truck is a special kind of construction machinery to realize the rapid transportation and pouring of concrete, widely used in transportation, energy, construction, national defense and other fields [1; 2; 3]. The concrete pumping system (CPS) is the core unit of concrete pumping trucks, and its performance directly affects the pumping distance and efficiency of concrete flow [4]. The CPS mainly includes the pumping mechanism and the swing mechanism, which realize the continuous delivery of concrete through the reciprocating action of the pumping cylinder and the swing cylinder. Timing matching refers to the coordination of the action of the pumping cylinder and the swing cylinder, which affects the pumping efficiency, impact vibration and service life of vulnerable parts. The existing CPS still has problems such as the large impact of pumping reversal, poor reliability of pumping operation and low pumping efficiency [5; 6].  
As concrete is enclosed in pipes and difficult to observe, the combination of simulation and experimentation is an important tool to study the flow and pumping characteristics of concrete [7]. [PERSON] et al. [8] established a 3D model of a concrete pump truck conveying pipe, simulated the concrete pumping process by a CFD-DEM model and investigated the relationship between structural parameters and pressure loss. [PERSON] et al. [9] investigated the changes in concrete properties during pumping and the formation of lubricating material under pressure. [PERSON] et al. [10] studied the effect of the coarse aggregate size onpipe flow of pumped concrete. [PERSON] et al. [11] established a virtual prototyping simulation platform for concrete pump trucks based on ADAMS, AMEsim and MATLAB, analyzed the boom system of the pump truck and obtained system coupling levels. The swing unit is one of the core units of the pumping system. Its main role is to quickly and smoothly drive the oscillation of the distribution valve to match the pumping cylinder to change direction, and its dynamic characteristics directly affect the efficiency, reliability and smoothness of the pumping machinery. [PERSON] et al. [12] and [PERSON] et al. [13] established a pumping system simulation model based on AMEsim software that can more accurately reflect the changes in accumulator pressure, commutation speed and law and save a lot of test costs. To address system pressure shocks during rapid oscillation, [PERSON] et al. [14] analyzed the buffering characteristics of parabolic buffers, and [PERSON] et al. [15; 16] optimized the buffering structure of the oscillating cylinder. [PERSON] et al. [17] studied the dynamic characteristics and operating rules of pumping systems. [PERSON] et al. [18] used a double reversing valve with an accumulator to suppress hydraulic shocks of the pumping system. [PERSON] et al. [19] proposed a new structure of a variable-speed direct-drive pumping system, established it mathematical model and simulation model and obtained precise control for the concrete cylinder by active disturbance rejection control. These literatures provide useful references for the study of pumping hydraulic systems.  
Concrete pumping is an interesting topic, but traditional studies focus mainly on concrete materials. This study does not deal with concrete materials but focuses on the operating laws and optimization of pumping hydraulic systems. The current research has the following shortcomings: the model of the pumping system is not accurate enough, resulting in a simulation model that does not truly reflect the dynamic characteristics of the actual system; there is a lack of joint analysis of the pumping and swing units; and the commutation timing of the two does not match, which results in serious erosion and wear of wearing parts. This paper establishes an accurate simulation platform based on experiments, and studies the operation law and commutation timing matching to reduce erosion and wear. This paper will provide a reference for the design and optimization of the CPS.