Abstract: To effectively control unbalanced vibration caused by grinding wheel mass unbalance, a new active control strategy for grinding wheel unbalanced vibration is proposed in the paper, the controllable electromagnetic force which is used to suppress vibration in control scheme originates from the principle of a bearingless motor having a radial magnetic force generation. First, induction electric spindle radial control force model and the force model which is exerted on grinding wheel are analyzed. And then, the dynamic model of induction-type flexural electric spindle-grinding wheel is modeled using finite element method. Finally, an active unbalanced vibration control system for electric spindle-grinding wheel is designed and simulated. The results show that the control scheme has significant effect on suppressing the unbalanced vibration of grinding wheel.
Abstract: In order to further reduce the vibration transmitted from vehicle to driver, a new model of driver scissors linkage seat suspension was put forward, in which an air spring with auxiliary chamber and a MR damper are between the face and floor of the seat. The motion differential equation of this seat suspension system was established and the theoretical computing formulation of it’s equivalent vertical stiffness, equivalent damping coefficient, natural frequency and damping rate were deduced. Besides, taking HY-Z04 scissors linkage seat, SK37-6 air spring of ContiTech and RD-1005-3 MR damper of LORD as an example, the equivalent stiffness and damping coefficient in different conditions of the air spring pressure, the sprung mass, the orifice diameter and MR damping were computed and analyzed. The study results show that the air spring pressure, the sprung mass, the orifice diameter and MR damping all have obvious influence on the equivalent stiffness and damping coefficient, so the seat comfort can be improved by changing the air spring pressure, the orifice diameter and MR damping according to driver’s weight and road condition.
Abstract: Aeroengine oil contains wear debris generated by friction. Based on the Dempster-Shafer evidence combination theory, aeroengine wear conditions can be effectively diagnosed. Through analysising the elements of wear debris in lubricating meduim, it can determine engines wear levels and wear parts, as references for troubleshooting. In the process of combination, an method was proposed that every element of wear quantity and wear rate were fused at first,then the integration of all elements. For Dempster-Shafer has its own limitations, two impoved methods were applied to and were compared. The results show that Dempster-Shafer evidence combination is an effective fault diagnosis method for aeroengine oil wear condition.
Abstract: Noise, bistable system and input signal are the three essential factors in stochastic resonance (SR). The noise-induced SR method, the parameter-tuning SR method, and the twice sampling SR method change the characteristics of the noise, the bistable system and the input signal, respectively. With the new cooperation, they can all produce the SR phenomena when the system exceeds the small-parameter area. If treating the strong noise and the input signal with large frequency, the actions of the system parameters can build the system behavior in an orderly way, associated with the twice sampling frequency. The united parameter-tuning SR method adjusts the system parameters to fit the normalized frequency after the twice sampling SR, in order to make the optimal noise intensity. The application to the flow meter vibration test has presented the practicability and effectiveness of the united parameter-tuning SR method.
Abstract: In this paper, a novel precision press is proposed, which is to combine the motion of a large constant speed motor with a small servomotor via a two-DOF mechanism, where, the constant speed motor provides main torque and motion requirements, while the servomotor contributes to modulations on this motion. The forward kinematic optimal design, electromechanical system dynamics modeling and simulation of this new mechanical press system have been presented here. The simple analysis of theoretical feasibility of the hybrid-driven press is investigated.
Abstract: Multi-exciter vibration can provide greater thrust for overweight test specimen, achieve the uniformity of vibration for the special structure of the thin specimen, and overcome the shortcomings in single-exciter test, it becomes the trend of vibration test. Based on the control theory of multi-exciter vibration test, a system equilibrium synthesis is presented to make up for deficiencies of different methods for random vibration test control algorithm. the relevant experimental study is carried out on the experimental platform, experimental results show that dynamic control range of multi-exciter random vibration control system achieves 90dB in the self closed-loop control test. high precision is reached for self-spectrum control of actual test system after establishing multiple shaker, self-spectrum of control response is controlled in the range of ± 1.5dB, which satisfies requirements in engineering test.
Abstract: Modern and reliable tightening spindle systems are indispensable due to importance of bolt connection in assembly technology, and the tightening spindle system is developed in order that automated tightening processes is able to ensure uniform quality of the tightened bolt connection. In this paper, the strategy “torque control and angle checked” of tightening is discussed and analyzed on the basis that the process mechanism of forming bolt connection is clarified. This strategy builds the base and boundary conditions of modular design strategy for tightening spindle system which is introduced, because it makes design flexibly, and many standard components can be chosen with more efficiency and low cost. The module partition bases on the function of the components of the system. The possibility of expansion of the tightening system comes into discussion too.
Abstract: In this paper, there are two kinds of impact vibration models: rigid impact model and elastic model. The dynamic responses of the two kinds of gear impact models are compared by experimental and numerical analysis. Firstly, establish the motion equations of the two models. Secondly, verify the correctness of the mechanical models through experimental analysis. Comparing the results of the numerical and experimental analysis, we can find that the intensity noise of gear vibration is reduced by the elastic boundary. Finally, the dynamic bifurcation characteristic of dimensionless excitations magnitude and backlash will be analyzed as well.
Abstract: Focusing on low-frequency shaking of the construction machine cab, the article analyzes reasons of the shaking and shows several improved isolator designs to reduce the effect of shaking on drivers’ comfort. Firstly according to previous 4 modes below 26 Hz from the finite element analysis of an excavator cab with 6 cab mounts, reasons for low-frequency shaking are analyzed. Then two improved measures of isolator designs for keeping the shaking small effectively are considered. Static analysis on one silicone-oil-sealed-type rubber mount, which can improve drivers’ comfort effectively according to practical application, is done. Besides, perfect setting approaches of isolators can greatly alleviate the cab shaking, which is confirmed by finite element modal analysis of the excavator cab, the first natural frequency of cab increased to 15.55Hz from 6.91Hz.