Design Of Force Sensing Fast Tool Servo System And Its Verification Through Cutting Experiment

The force measurement function is integrated in the fast tool servo(FTS),which can sense the interaction information between tool and workpiece in the cutting process.In this dissertation,the double end fixed quartz tuning fork is used as the force sensitive unit to design the FTS with force sensing ability,which can realize the purpose of cutting force measurement in the process of FTS machining.Based on the force measuring principle that the resonant frequency of the double end fixed quartz tuning fork is approximately linearly related to its axial force,a resonant force sensing unit based on the quartz tuning fork is integrated into the FTS,and the robust measurement of the three-axis cutting force is realized by reasonably arranging the position of the quartz tuning fork.Based on the elastic beam theory and the flexibility matrix method,the force frequency analytical modeling of force sensing unit of force sensing FTS is carried out.From the sight of strength constraints of quartz tuning fork and FTS body,the measuring range of force sensing FTS is theoretically analyzed.The analytical results are compared with the finite element analysis,and the modeling error is less than 10%,and the accuracy of the analytical model is demonstrated.A multi-objective and step-by-step optimization method for determining the key structural parameters of force sensing FTS is proposed.The optimization objective function is constructed by weighing the large stroke against high natural frequency and high force measurement resolution against high output stiffness.The differential evolution algorithm is used to optimize the design of force sensing FTS in two steps.Based on the optimized parameters,a prototype is manufactured for experimental verification.The stroke of force sensing FTS is 9.25 μm,the natural frequency is 4307 Hz,and the motion resolution is 8 nm.The sensitivity of the measured main cutting force,feed force and back feed force is 42.935 Hz/N,33.791 Hz/N and 3.621 Hz/N respectively.The force sensing FTS has good consistency with the force measured by the Kistler force sensor,and the force perception accuracy of the force sensing FTS is verified.Finally,the ability of the designed force sensing FTS to perceive the cutting process force is verified by the experiments of constant depth and sinusoidal depth scratches.The results show that when the cutting depth is 0.925 μm and 1.85 μm,the main cutting force is 3 N and 5 N respectively,and the back feed force is 0.5 N and 0.6 N respectively.