Jianfeng Tao

Milling Stability Prediction with Multiple Delays via the Extended Adams-Moulton-Based Method

The occurrence of machining chatter may undermine the workpiece surface quality, accelerate the tool wear, and even result in serious damage to the machine tools. Consequently, it is of great importance to predict and eliminate the presence of such unstable and detrimental vibration. In this paper, we present an extended Adams-Moulton-based method for the stability prediction of milling processes with multiple delays. Taking the nonuniform pitch cutters or the tool runout into account, the regenerative chatter for milling operations can be formulated as delay differential equations with multiple delays. The dynamics model for milling regenerative chatter is rewritten in the state-space form. Dividing the spindle rotation period equally into small time intervals, the delay terms are approximated by Lagrange interpolation polynomials, and the Adams-Moulton method is adopted to construct the Floquet transition matrix. On this basis, the milling stability can be derived from the spectral radius of the transition matrix based on Floquet theory. The calculation efficiency and accuracy of the proposed algorithm are verified through making comparisons with the semidiscretization method (SDM) and the enhanced multistage homotopy perturbation method (EMHPM). The results show that the proposed method has both high computational efficiency and accuracy.

A review of powered wheel for aircraft

To reduce noise, emission and fuel consumption of aircrafts taxiing at airport, powered wheel on landing gear was investigated experimentally and theoretically. The configurations of powered wheel driven by hydraulic motor and electric motor were proposed historically. Roll friction transmission, gear reducer transmission and direct transmission were adopted. With the global environmental problem and energy crisis being more and more prominent, powered wheel becomes one of the focuses of aviation industry again. This paper reviewed the background, history and current status of powered wheel for aircraft, and summarized its research emphases and development trend. The findings of our work showed that powered wheels for aircraft can reduce noise, emission and fuel consumption of aircraft at airport remarkably, and those driven directly by in-wheel electric motors installed on nose landing gears are the most promising wheels.

Influence of vibration on the performance of tunnel boring machines

Vibration in a hard rock tunnel boring machine (TBM) during tunnel excavation has been thought to have significant influence on TBM performance, in particular its excavation efficiency. This paper presents a study on this issue. A dynamic model of TBM is established to derive its vibration response, considering not only both of cutterhead driving system and thrust system, but also the interaction between shield and tunnel invert which is modeled by a 3D Winkler foundation with uniformly distributed damping springs and sliders. Based on the obtained vibration response of an opening TBM under simulated rock breakage forces, the influence of vibration on critical performance of TBM, including energy efficiency of rock breakage, disc cutter wear rate and interaction between shield and tunnel invert, is investigated. The results show that energy efficiency of rock breakage decreases with increasing of kinetic energy and potential energy in TBM, especially with sharp rise of dissipated energy due to friction occurrence under large vibration circumstance. A large margin increment of disc cutter wear rate is brought about by TBM vibration. Different with the results in energy efficiency and disc cutter wear rate, strong vibration induced axial force between shield and tunnel invert could make the whole TBM pushed forward more easily than in static contact. This study provide a reference for comprehensive evaluation of vibration of a TBM and its rock-breaking.

Stiffness modeling of thrust cylinder in hardrock tunnel boring machine

The thrust system of TBM propels the cutter head boiling forward and the strong impulse loads on propelling cylinder cause serious vibration problems. Based on the typical thrust system which the thrust cylinders are controlled by pressure reducing valves, the paper obtained the dynamic velocity stiffness, static velocity stiffness, minimum velocity stiffness of the thrust cylinder. According to the frequency distribution of dynamic velocity stiffness, it was concluded that load damping directly affect the static velocity stiffness. In middle frequency range, because of the oscillation order, there is a attenuation, which need to be compensated in the stiffness design; otherwise in high frequency range, velocity stiffness can be simplified into a first-order differential element. It can also be ascertained that the static velocity stiffness decides the break frequency. Simulation results verify the conclusions above.

Flow model and dynamic characteristics of a direct spring loaded poppet relief valve

This paper is concerned with the flow model and dynamic characteristics of the poppet relief valve. The flow model of the poppet valve orifice is established with a novel function of flow discharge coefficient, and the dynamic model including the aforementioned flow model of the poppet valve is established with consideration of the fluid forces caused by the valve body motion and the flowrate variation. Both the simulated and measured results of the dynamic response of the poppet relief valve shows that the experimental and simulation results are in fine accordance with each other in the perspective of the general shape of response, which confirm that the dynamic model of the poppet relief valve proposed in this paper is both accurate and efficient.

Modelling and simulation of unidirectional proportional pump-controlled asymmetric cylinder position control system with model predictive control algorithm

Unidirectional proportional pump-controlled asymmetric cylinder systems are widely used on industry machines, but the analysis and synthesis of such systems is very hard due to the nonlinearity caused by the different working areas of cylinder piston. The limit of one-way flow control ability of the pump and the working pressure make the problem more complex. It is very hard to find an effective method to solve this problem with the existing theory of electro-hydraulic servo control. To simplify the analysis and realize the no overshooting position control, this paper presents a third order state-space model with input and output constraints to depict the dynamic behavior of the system. A specially designed model predictive controller is used to guarantee that the output of the system has no overshooting. The results of the simulation experiments show that the proposed method can realize the high precision position control under multiple constraints effectively.

A novel approach for the acquisition of vibration signals of the end effector in robotic drilling

In terms of flexibility and versatility, the robotic drilling seems a promising solution for the large quantities of holes of aircraft structural parts. However, the low stiffness of the robots may induce chatter vibration in the drilling process, which results in poor surface quality and low machining productivity. Therefore, it is of vital importance to detect and prevent this undesirable instability. In this paper, an approach is presented for the acquisition of vibration signals of the end effector in robotic drilling. To begin with, the robotic drilling system is presented. Then the motion of the end effector is decomposed into the translation motion along the spindle and the plane motion perpendicular to the spindle. With the aid of the rigid body kinematics, the vibration signals of the end effector can be obtained through two triaxial accelerometers with the proposed method. Finally, the effects of accelerometer location and orientation errors are analyzed. The simulation results show that the measurement results are sensitive to both location and orientation errors.

Stability analysis of pump-controlled dual-winch system with PI controller

As for the synchronization control of dual winches of large crawler cranes, a master-slave PI control algorithm with the hooks inclination as feedback signal is proposed and analyzed. The transfer function of the pump-controlled dual-winch system is obtained by building the mathematical model and linearizing it around the working point and thus the stability can be analyzed. The way to determine the parameters of PI controller is proposed via frequency response method. The research indicates that the proposed control algorithm is able to guarantee the steady-state error to be zero and that the stability of the whole system depends on the stability of the hydraulic subsystem and the actuator subsystem. Specifically, the stability of the hydraulic system can be ensured by increasing leakage and the stability of the actuator can be improved through PI controller.

Design of integrated architecture of Web Service-Based diagnosis system for TBM

Tunnel Boring Machine (TBM) is widely utilized in tunnel construction. Effective fault diagnosis of TBM is vital for the safety of tunnel boring since the failure of TBM might cause harm for the workers accompanying with the loss of time and economy. A Web Service-Based Remote Diagnosis System (WSRDS) with Bayesian network (BN) as the faults analysis model is proposed in this paper. BN is a concise, practical and intuitive method to determine the exact cause for failure. The WSRDS enables an easy access for the diagnosis system of TBM and highlights an enhancement to the ubiquitous information processing. Taken the thrusting system of TBM as an example, the architecture of the WSRDS is formulated and the function of every module is described. The key system modules including general diagnostic procedure and integrated design of the diagnostic database are elaborated. The WSRDS could effectively realize the data integration among distributed enterprises of heterogeneous systems and greatly improves system reusability. The proposed WSRDS might have a promising wide application in the maintenance of TBM.

Internal leakage characteristics of gripper cylinder of TBM

This paper is concerned with the internal leakage characteristics of the gripper cylinder in Tunnel Boring Machine (TBM) under impact load. The internal leakage model of the gripper cylinder included factors such as the clearance between the piston and the internal wall of the cylinder, as well as the moving amplitude and frequency of the gripper cylinder is established. Due to the leakage model, the influences of the aforementioned parameters on the leakage characteristics are analyzed. The analysis indicates that the moving amplitude and the frequency of the gripper cylinder both have remarkable influences on the internal leakage of the gripper cylinder, the internal leakage flow rate will be negative when the frequency is greater than 120 rad/s as the clearance is 0.01 mm. The peak value of the pressure in rod chamber increases while the amplitude is declining with the clearance.