Biological compound-eye systems have unique advantages in three-dimensional (3D) positioning based on light energy distribution. A curved compound eye was designed and manufactured to imitate a biological compound eye. To overcome the nonuniform off-axis response and enlarge the aperture of the eyelet, a novel dome light cone was designed. The dome light cone was designed as a conical structure, which consisted of a lot of fiber wires with a diameter of 6 μm. Additionally, based on the proposed biological compound-eye systems, an algorithm was proposed to obtain the 3D position of the object by analyzing the light location and intensity distribution. The effect of the illumination intensity, the position of the target’s center, and the non-repeatability were evaluated. The relative standard uncertainty in the 3D position was estimated to be 8.6%. Low uncertainty verified the validity of the 3D localization algorithm.

To achieve a system combining large field of view (FOV), high image quality, high 3D detection accuracy, and high-speed tracking in a close shot, a single-layered compound eye with seven ommatidia is developed. The functional relationship among the FOV, optical axis angle, and overlapping area is established mathematically. Based on the relationship, one center ommatidium and six hexagonally arranged marginal ommatidia with large apertures are set on a spherical substrate to guarantee a large FOV and sufficient overlapping information for 3D imaging. To control the off-axis aberration of the marginal ommatidia, an optical freeform surface is applied. The algorithms of regions of interest and Kalman filter are applied to achieve high-speed capturing. Experiments show that the system can obtain a high-quality image with sufficient overlapping information for 3D tracking in shifting distance.

Knee Osteoarthritis (KOA) is a prevalent condition worldwide, significantly diminishing quality of life and productivity. Except for the alignment change, muscle activation patterns (MAP) have garnered increasing attention as another crucial factor contributing to KOA. This study explores the factors, characteristics, and effects of MAP changes caused by KOA, providing a neuromuscular-based causal analysis for the rehabilitation treatment of KOA. Keywords including the association of MAP with KOA will be included. “Knee, Osteoarthritis, Electromyography(EMG), Muscle Activity patterns, activation amplitudes, activation time, Muscle Synergy, Co-contraction/activation” were used to search the databases of Science Direct, PubMed, Scopus, and Wiley. The criteria include studies from the past fifteen years that document changes in muscle contraction characteristics and causality analysis in patients with KOA. we compared MAP changes between individuals with and without KOA, such as the activation amplitudes, activation time, muscle synergy and co-contraction index(CCI). Additionally, we explored the potential relationship between muscle weakness, pain, and lower limb mechanical changes with the variations of MAP. A total of 832 articles were reviewed, and 44 articles that met the inclusion criteria were selected for analysis. The changes in biomechanical structure, pain, and muscle atrophy may contribute to the formation and progression of the changes in MAP in KOA patients. In moderate KOA patients, the vastus lateralis (VL) and biceps femoris (BF) exhibits larger activation amplitudes, with earlier and longer activation times. The vastus medialis (VM) shows a delayed activation time relative to VL. Gastrocnemius activation time is prolonged during mid-gait, while the soleus exhibits lower activation amplitudes during the late stance phase. There are fewer, merged synergies with prolonged activation coefficients, and a higher percentage of unclassifiable synergies. Additionally, the CCI is positively correlated with task difficulty and symptoms. It is higher in the medial and lateral than hamstrings and quadriceps, and CCI specifically respond to joint stabilisation and load. In patients with moderate KOA, changes in MAP are mainly related to symptoms and the difficulty of tasks. MAP changes primarily result in variations in amplitude, contraction duration, muscle synergy, and CCI. The MAP changes can subsequently affect the intermuscular structure, pain, joint loading, and stiffness. These contribute to the progression of KOA and create a vicious cycle that accelerates disease advancement. Clinical rehabilitation treatments can target the MAP changes to break the cycle and help mitigate disease progression.

Haptics plays an important role in grasping and manipulating objects for human hands and artificial robotic hands. The density of tactile receptors at the tips of the fingers is very high, reaching 140 units/cm ² . However, the density of the existing tactile sensors is very low. To increase the density of the 3-D tactile sensor, a novel high-density arrayed and curved 3-D tactile sensor based on bionic compound eye with the density up to 42 units/cm ² is proposed in this article. The tactile sensor can detect both normal force and shear force since it is isotropic. The force measurement setup has been successfully built with a sensitivity of 0.000280 mN/Gray for normal force and 0.0262 N/ μm for shear force. The sensor will provide a technical basis for force measurement of surgical robots and manipulators.

A micro/nano force can be traced to the International System of Units by means of an electrostatic force balance weight system. However, the micro/nano force measurement system is susceptible to environmental disturbances. Various methods have been proposed to reduce the effect of environmental disturbances and obtain high resolution and fast response. In this paper, we introduce a combination of air damping and inherent damping from the internal molecular friction of spring suspension. This will optimize system stability and improve environmental noise suppression. Results from the air damping model show that the damping ratio increases from 0.0005 to 0.1, which improves the vibration resistance. We found that the system with air damping has the advantages of fast response and low scatter.

Force in the micronewton range may be traced to the International System of Units by an electrostatic force balance weight system. However, there is a conflict between range and sensitivity. To solve this problem, a lever-type force metrology system based on the null-balance method is reported. The force is loaded on one end of the lever, causing elastic torsion of the central rod, and an electrostatic force is applied to the other end. With a variety of mass loading positions and standard weights, a wide range of moments may be produced to calibrate the system. The electrostatic force was generated by a pair of coaxial cylindrical capacitors where the applied voltage was converted into electrode displacement. The design of the inner and outer cylindrical capacitors was deduced considering the material and miniaturization requirements, and concentric alignment was ensured by a vision system. The null balance was achieved by a proportion-integration-differentiation control system, so that the external force was compensated by the electrostatic force. A method to increase the center of gravity was used to improve the resolution. The mechanism was analyzed based on stiffness, strength, stability, and frequency. Furthermore, the impact on the capacitance gradient due to the capacitor tilt caused by the applied force was estimated. Standard weights were utilized to evaluate the system performance. The results showed that a stiffness of 0.8 N/m and a force resolution of 10⁻⁸ N were achieved.