An augmented formulation of distributed compliant mechanism optimization using a level set method

Topology optimization has emerged as one of the key approaches to design compliant mechanisms. However, one of the main difficulties is that the resulted compliant mechanisms often have de facto hinges. For this reason, a simple yet efficient formulation for designing hinge-free compliant mechanisms is developed and examined within a level set–based topology optimization framework. First, the conventional objective function is augmented using an output stiffness. Second, the proposed formulation is solved using a level set method for designing some benchmark problems in the literature. It is shown that the proposed augmented objective function can prevent the de facto hinges in the obtained compliant mechanisms. Finally, some concluding remarks and future work are put forward

Mechanical Structural Design of a Piezoresistive Pressure Sensor for Low-Pressure Measurement: A Computational Analysis by Increases in the Sensor Sensitivity

This paper proposes a novel micro-electromechanical system (MEMS) piezoresistive pressure sensor with a four-petal membrane combined with narrow beams and a center boss (PMNBCB) for low-pressure measurements. The stresses induced in the piezoresistors and deflection of the membrane were calculated using the finite element method (FEM). The functions of the relationship between the dimension variables and mechanical performance were determined based on the curve fitting method, which can provide an approach for geometry optimization of the sensor. In addition, the values in the equations were varied to determine the optimal dimensions for the proposed membrane. Then, to further improve the sensitivity of the sensor, a series of rectangular grooves was created at the position of the piezoresistors. The proposed diaphragm was compared to existing diaphragms, and a considerable increase in the sensitivity and a considerable decrease in nonlinearity error could be achieved by using the proposed sensor. The simulation results suggest that the sensor with the PMNBCB structure obtained a high sensitivity of 34.67 mV/kPa and a low nonlinearity error of 0.23% full-scale span (FSS) for the pressure range of 0–5 kPa. The proposed sensor structure is a suitable selection for MEMS piezoresistive pressure sensors

Error modeling and calibration of a 4ṞRR redundant positioning system

Using the macro-micro combination positioning system for nanomanipulating can fulfill the requirements of large workspace, high precision and multi-degrees of freedom. As a macro part of the macro-micro combination positioning system, a redundantly actuated three degrees-of-freedom (DOF) parallel kinematic mechanism (4ṞRR) with a directly driven system is studied in this paper. Firstly, the error sensitivity of the 4ṞRR planar parallel mechanism is analyzed with global errors sensitive index (GESI) based on the error model of the positioning system. Then, a novel and practical calibration method combined with an error compensation strategy is proposed for the 4ṞRR positioning system. Finally, in order to verify the proposed method, a series of experiments are conducted with the laser measurement system in creditable conditions, and the data are illustrated for comparisons. The experimental results show that the positioning accuracy of the 4ṞRR positioning system is improved, and the performances of the end-effector are enhanced based on the proposed method

A local optical flow eye-tracking method for depression detection

Aiming at the problem that depression detection is easily affected by subjective factors such as patient willingness, self-awareness, and doctor’s level, as well as inconvenient detection and high cost, a universal detection method with low cost and convenient deployment is proposed. A local optical flow tracking method is adopted, which is realized by eye region detection and optical flow estimation. Then, three experiments are designed to verify the accuracy of the method and the effectiveness of eye movement tracking. The formula for calculating the depression state is proposed, and the eye movement of one normal participant’s elliptical trajectory of the left and right pupils in the horizontal and vertical directions is 44.4805, 42.7013, 29.3571, and 31.1364 mm, respectively. To verify the effectiveness of the proposed method, three example points are selected. Among them, the fixation duration at P1 is 1.87 s, the eye movement direction at P2 and P3 is 1.168°, counterclockwise around the X axis, and the number of fixation times is 46. Finally, 18 normal participants and four depression-positive participants are tested by the exploratory eye movement paradigm. The results show that the accuracy rate of identifying depression patients using the NEF metric method can reach ∼81.8%, which can help quantify the detection of depression and provide the possibility for professionals to remotely diagnose individuals with depression