| In precision grinding processing,high-speed machining is often adopted to obtain better product processing accuracy and surface quality.As grinding speeds and grinding accuracy increase,even slight imbalances on the grinding wheel can generate large unbalanced centrifugal forces,which can seriously affect machining accuracy.The classical offline dynamic balancing technology is time-consuming and difficult to meet modern production requirements,while the online active balancing technology can achieve balancing during spindle rotation with short balancing time and high precision,which meets the requirements of modern automated intelligent manufacturing.The new electromagnetic online active balancing controller has the advantages of small axial size and fast balancing response,which is suitable for high-speed machining and is the most promising online dynamic balancing control technology at present,but there are no mature commercial products for high-speed precision grinding machining in China.For this reason,this paper carries out the structural design,performance prediction and development of the online dynamic balancing control system,and the main work completed is as follows:(1)Considering the radial air gap and axial air gap of the electromagnetic balancing head,the theoretical formulae for the electromagnetic driving force and permanent magnet self-locking torque are derived and the results of the self-locking torque calculation are compared with the finite element analysis results,which show that the analytical solution is large compared to the finite element calculation results,but the error is within 20%.(2)The design of the counterweight plate of the electromagnetic automatic balancing device has been improved to solve the problem of the counterweight plate touching the magnetic tooth discs on the left and right sides due to the deflection of the counterweight plate during operation and to achieve the goal of stable operation of the counterweight plate.(3)To address the problem of permanent magnet self-locking,the ANSOFT MAXWELL finite element software was used to establish a model for the analysis of the permanent magnet self-locking magnetic circuit of the balancing head.The influence of parameters such as the number of permanent magnets and axial air gap on the self-locking torque was analysed,and the optimal parameters were selected by combining the machining and assembly processes.(4)A LabVIEW-based vibration dynamic balancing test and analysis system was developed to achieve accurate acquisition of the amplitude and phase of unbalanced vibration signals by means of whole-cycle sampling and FFT transformation,and data exchange with the STM32 through a designed serial data transmission platform to realise the issuance of control commands for online real-time automatic control.The power transmission system was designed to achieve the purpose of simulating the unbalanced working condition of the grinding wheel during the grinding process,and the online active dynamic balancing comprehensive experimental system platform was developed.(5)Based on the developed comprehensive test system,the self-locking torque test was carried out.The peak self-locking torque decreases with the increase of air gap,and the finite element analysis value is slightly larger than the test value,but the overall error is kept within15%,which is in line with the general engineering requirements and indicates that the simulation calculation value is reasonable.A mass block was added to the disc to simulate the amount of unbalance generated during the operation of the grinding wheel,and the vibration change before and after balancing was calculated by the vibration test system developed to verify that the online dynamic balancing active control system has good balancing capability.The test results show that the dynamic balancing system can achieve a balance quality of about G0.4 for a rigid rotor after balancing. |
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