The surface/subsurface damage of engineering ceramics after machining has a great influence on the service performance of parts. In order to obtain a high grinding surface quality of engineering ceramics, and take silicon nitride ceramic as a research object, a series of grinding experiments were carried out. The effects of grinding parameters on longitudinal crack propagation depth and the surface residual stress of silicon nitride ceramics were analyzed by grinding experiments, and the residual stress at the location of crack propagation was obtained. The variation in the grinding temperature under different grinding parameters was explored. The influences of the grinding temperature on crack propagation depth and surface residual stress were clarified, the distribution of residual stress along the depth direction was discussed, and the relationship between the residual stress and crack propagation was revealed. The results show that the residual compressive stress on the surface of silicon nitride ceramics decreases with the increase in the depth of crack propagation and the degree of surface brittle spalling. The residual stress at the location of the crack propagation was residual tensile stress. The crack propagation depth increased with the increase in the residual tensile stress. The research provides a reference for the realization of high-quality surfaces in the grinding of silicon nitride ceramics.

Inverse kinematics of redundant robots presents a challenging problem for real-time applications due to the lack of uniqueness of solution and the low computational efficiency caused by redundancy and hard limits. In this work, a general and efficient method for addressing the real-time optimized inverse kinematics of redundant robots is proposed, taking into account hard limits in joint and Cartesian space that can never be violated. The proposed method proceeds by using constrained linear programming instead of quadratic programming to solve the inverse kinematics problem. Various hard limits such as joint range, bounds on velocity and acceleration are handled explicitly as inequality constraints. This method resolves the redundancy in real-time and enable to simultaneously guarantee that the additional motion constraints will never be violated. Its performance allows real-time kinematic control of redundant robots executing sensor-driven online tasks. The effectiveness of this method is demonstrated through simulations and experiments conducted on a 7-DOF KUKA IIWA robot, showcasing its ability to control redundant robots executing sensor-driven tasks in dynamic environments with numerous hard limits.

In this paper a class of generalized piecewise smooth maps is studied, which is linear at one side and nonlinear with power dependence at the other side. According to the value of the power in the term $x^z$, the bifurcations occurring in this map are classified into five types: $z>1$, $z=1$, $0<z<1$, $z=0$, and $z<0$. We derive the occurrence conditions of border collision bifurcation and smooth fold and flip bifurcation, especially the codimension-2 bifurcation points describing the interaction between border collision bifurcation and smooth bifurcation. The general results are then applied to the specific cases of the power $z$, and different bifurcation scenarios are shown for individual cases, from which the period-adding scenario is found to be general for any power.

Traditional body-centered cubic (BCC) lattice metamaterials exhibit structural deficiencies including geometric discontinuity at cell connections and pronounced stress concentration at nodal regions, which restrict further enhancement of mechanical performance. This study proposes a novel lattice design methodology utilizing trigonometric function-modulated strut axes, yielding three novel trigonometric function curved rod cell-based lattice structures (TCRC, SCRC, and CCRC). By integrating fillet transition technology to achieve stress redistribution optimization, these configurations were systematically upgraded to TCRC-ipv, SCRC-ipv, and CCRC-ipv variants with enhanced structural performance. Experimental specimens were fabricated using selective laser melting (SLM) additive manufacturing technique, and the static mechanical response mechanisms were systematically investigated through quasi-static compression tests coupled with nonlinear finite element method (FEM) simulations. Results demonstrate that the trigonometric function-based topology optimization strategy combined with nodal fillet design significantly enhances overall structural performance. The TCRC-ipv configuration exhibits optimal comprehensive mechanical properties: compared with the reference BCC structure, it achieves 39.2% enhancement in elastic modulus, 59.4% increase in peak compressive strength, and 46.1% improvement in yield strength. Additionally, the energy absorption stress plateau elevates by 10.3%, with specific energy absorption capacity remarkably augmented by 86.1%. The proposed multiscale collaborative optimization strategy establishes a new theoretical framework and technical pathway for topology optimization design of lattice metamaterials in engineering applications.

Rolling bearings are key elements in rotating machinery, and reliable fault diagnosis is crucial for condition monitoring and maintenance decisions. Under strong background noise, vibration signals are easily distorted, which degrades conventional CNN-based diagnosis. To address this issue, an RSBU-MSCNN-based approach is proposed. First, Gaussian white noise with different signal-to-noise ratios is added to original signals to simulate industrial noise, and one-dimensional vibration signals are transformed into two-dimensional time–frequency representations using CWT. Then, a residual shrinkage module with a soft-threshold function is introduced for adaptive denoising and redundant noise suppression, while multi-channel, multi-scale convolutions enhance robust feature extraction across different receptive fields. Finally, faults are classified using fully connected layers. Experiments on multiple datasets show high accuracy under strong noise, confirming the robustness and applicability of the proposed method for industrial maintenance.