This study presents a new robust formulation for the topology optimization of compliant mechanisms, addressing the design challenges while considering manufacturability, static strength, and fatigue failure. A three-field density projection is implemented to control the minimum size of both real-phase and null-phase material structures to meet the manufacturing process requirements. The static strength is evaluated via the sum of the amplitude and the mean absolute value of the signed von Mises stress. The fatigue failure is solved via the modified Goodman criterion. The real output displacement is optimized by adding artificial springs to the prescribed value. This approach is implemented based on an improved solid isotropic material with penalization (SIMP) interpolation method to describe and solve the optimization model and derive the shape sensitivity of the optimization problem. Finally, two numerical examples are applied to illustrate the effectiveness of the presented method.

Three-dimensional elliptical vibration cutting (3D-EVC) is one of the machining methods with the most potential in ultra-precision machining; its unique characteristics of intermittent cutting, friction reversal, and ease of chip removal can improve the machinability of materials in the cutting processes. However, there is still not much research about the chattering phenomenon in the 3D-EVC process. Therefore, based on the empirical mode decomposition (EMD) technique and feature extraction, a chatter identification method for 3D-EVC is proposed. In 3D-EVC operations, the vibration signal is collected by the displacement sensors and converted to frequency domain signal by fast Fourier transform (FFT). To identify tool cutting state using the vibration frequency signal, the vibration signals are decomposed using empirical mode decomposition (EMD), a series of intrinsic mode functions (IMFs), so the instantaneous frequency can be reflected by the vibration signals at any point. Then, selecting the primary IMFs which contain rich chatter information as the object in feature extraction identification, and two identification indexes, that is, the mean square frequency and self-correlation coefficient, are calculated for the primary IMFs by MATLAB software, to judge the chatter phenomenon. The experimental results showed that the mean square frequency and self-correlation coefficient of the three cutting states increase with the increase in the instability of the cutting state. The effectiveness of the improved chatter recognition method in 3D-EVC machining is verified.

A high-precision XY nanopositioning stage is developed by designing a novel normal-stressed electromagnetic actuator (NSEA) and compliant parallel mechanism (CPM). Unlike piezoelectric actuators, the designed electromagnetic actuator operates without physical contact. Unlike traditional bridge-type compliant mechanisms, the material distribution of the CPM is optimized using the bidirectional evolutionary structure optimization (BESO) method. The subchain of single-CPM is regarded as an independent design domain in topology optimization. This article extends the BESO method to the frequency optimization field, incorporating the constraints of the material volume and the global displacement. The theoretical models of the normal-stressed electromagnetic circuit and the compliant mechanism are established and systematically verified via finite element analysis. Besides, to realize the high-accuracy control, a Proportional-Integral-Derivative (PID) controller with a feedforward compensator is applied on each axis, which is then demonstrated by finely tracking of the Archimedean spiral and Lissajous trajectories.