Program design of an online dynamic balancing system for grinding-wheel and spindle
For unbalance of grinding wheel and spindle system in high-speed grinding process, an online dynamic balancing program is proposed. Firstly unbalance factors during grinding process are analyzed, and vibration features excited by these centrifugal forces are defined. Based on these works, technologies on wheel-spindle online dynamic balancing are introduced, including sensor selection and setting, vibration signal and phase angle measurement, signal amplification and analog filtering, A/D conversion, digital filtering, unbalance solution, dynamic balancing device and its drive and control. Finally, a wheel-spindle online dynamic balancing program is designed, which will have a good engineering application prospect in CNC machine spindle system.
Eccentricity Parameters Identification for a Motorized Spindle System Based on Improved Maximum Likelihood Method
As a kind of rotor system, the electric spindle system is the core component of the precision grinding machine. The vibration caused by the mass imbalance is the main factor that causes the vibration of the grinding machine. Identifying the eccentricity parameters in an electric spindle system is a key issue in eliminating mass imbalances. It is difficult for engineers to understand the approximate range of eccentricity by experience; that is, it is difficult to obtain a priori information about eccentricity. At the same time, due to the geometric characteristics of the electrospindle system, the material factors and the randomness of the measurement response, these uncertain factors, even in a small case, are likely to cause large deviations in the eccentricity recognition results. The search algorithm used in the maximum likelihood method to identify the eccentricity parameters of the electrospindle system is computationally intensive, and the sensitivity in the iterative process brings some numerical problems. This paper introduces an Advance-Retreat Method (ARM) of the search interval to the maximum likelihood method, the unknown parameter increment obtained by the maximum likelihood method is used as the step size in the iteration, and the Advance-Retreat Method of the search interval is used to adjust the next design point so that the objective function value is gradually decreasing. The recognition results under the three kinds of measurement errors show that the improved maximum likelihood method improves the recognition effect of the maximum likelihood method and can reduce the influence of uncertainty factors on the recognition results, and the robustness is satisfactory.
A Study on the Active Balancing for High-Speed Rotors (I): Development of the Active Balancing System
High speed rotating machines can be very sensitive to rotating mass unbalance that is a major source of harmful vibration for many types of rotating machinery. So, the balancing procedure is needed for all high-speed rotating system. To save the time and cost of off-line balancing, many researchers have developed the on-line balancing devices and methods. In this paper, an active balancing device, which is an electro-magnetic type, is developed and the active balancing algorithm using influence coefficient method is also proposed. The active balancing experiment for flexible rotors during operation is performed by an active balancing device. As a result, controlled unbalance responses are below the vibration limit at all rotating speed ranges with critical speed.