In this paper, a novel global time-varying path planning (GTVP) method is proposed. In the method, real-time paths can be generated based on tunable Bezier curves, which can realize obstacle avoidance of manipulators. First, finite feature points are extracted to represent the obstacle information according to the shape information and position information of the obstacle. Then, the feature points of the obstacle are converted into the feature points of the curve, according to the scale coefficient and the center point of amplification. Furthermore, a Bezier curve representing the motion path at this moment is generated to realize real-time adjustment of the path. In addition, the 5-degree Bezier curve planning method consider the start direction and the end direction is used in the path planning to avoid the situation of abrupt change with oscillation of the trajectory. Finally, the GTVP method is applied to multi-obstacle environment to realize global time-varying dynamic path planning. Through theoretical derivation and simulation, it can be proved that the path planned by the GTVP method can meet the performance requirements of global regulation, real-time change and multi-obstacle avoidance simultaneously.

Traditional methods for solving the inverse kinematics of a hyper-redundant manipulator (HRM) can only plan the path of the end-effector with a complicated solving process, where obstacle avoidance is also not considered. To solve the above problems, a novel method for solving inverse kinematics of HRM is proposed in this paper: the variable dimension scaling method (VDSM), which can solve complex inverse kinematics while avoiding obstacles. Through this method, the path of the end-effector is scaled under a certain proportion and is adjusted depending on the position of the obstacle, which has good universality. The number of link angles changed is as small as possible in the process of achieving the end-effector moving along the desired path. With the redundancy of HRM, obstacle avoidance can be implemented in any environment by the proposed method. Through simulation and experiments in different environments, the above advantages of VDSM are verified.

In bone-milling surgical procedures, the intense friction between the tool and bone material often results in high cutting temperatures, leading to the thermal necrosis of bone cells. This paper aims to investigate the effect of micro-texture on the tribological properties of YG8 cemented carbide in contact with bone. The main objective is to guide the design of tool surface microstructures to reduce frictional heat generation. To minimize experimental consumables and save time, numerical simulations are first conducted to determine the optimal machining depth for the texture. Subsequently, micro-textures with different shapes and pitches are prepared on the surface of YG8 cemented carbide. These textured samples are paired with bovine cortical bone pins featuring various bone unit arrangements, and friction and wear tests are conducted under physiological saline lubrication. The experimental results indicate that the appropriate shape and pitch of the micro-texture can minimize the coefficient of friction. The parallel arrangement of bone units exhibits a lower coefficient of friction compared to the vertical arrangement. This study holds significant implications for the design and fabrication of future micro-texture milling cutters.

Extremely low frequency (ELF, 3–30 Hz) signals possess strong cross-medium communication capabilities, making them particularly well-suited for underground and underwater environments. However, traditional low-frequency (LF) transmission systems are large and inefficient, posing significant limitations in practical applications. In recent studies, mechanical antennas have been explored to generate LF signals, but current approaches rely on bulky equipment with limited range, making them unsuitable for personal use or integration into small unmanned devices. To address this challenge, this study introduces a flexible, magnet-based miniaturized LF mechanical antenna, fabricated using 3D printing. The antenna consists of a macro-fiber composite layer and a flexible permanent magnet film, and features an extremely compact volume (<6.8 cm³) and low weight (<50 g). It is also highly flexible, allowing for easy integration into diverse applications. Its transmitted signal can reach 60 m before the magnetic field strength attenuates to 1 pT. Mounted on an unmanned aerial vehicle (UAV), the antenna facilitates reliable communication between quadruped robots operating outside caves and aerial robots located deep within cave interiors, where high-frequency (HF) signals cannot penetrate. This study demonstrates robust LF cross-medium communication between UAV and ground robots in cave environments, paving the way for unmanned collaboration in scenarios inaccessible to HF wireless signals.

To solve the time-optimal problem of velocity planning, various optimization-based methods were proposed in the literature, but these existing methods typically have limitations on completeness and real-time performance. For the scenario of single-axis multipoint (SAMP) motion, this article proposes a global dynamic programming algorithm with local greedy strategies to solve the time-optimal velocity planning problem, which is important for the multiaxis synchronous velocity planning problem. The proposed method, which is called SAMP algorithm, transfers the problem into the splicing problem of interval endpoints and acceleration. Then, based on the assumptions of continuity and monotonicity of piecewise polynomial functions, it derives the optimal motion mapping in these different intervals. Finally, the SAMP algorithm obtains the global time-optimal solution by employing the global dynamic programming with a backtracking algorithm. Simulation and experiments demonstrate that the SAMP algorithm not only has time optimization but also shows good numerical efficiency.