A multi-gas sensor system was developed that uses a single broadband light source and multiple carbon monoxide (CO), carbon dioxide (CO₂) and methane (CH₄) pyroelectric detectors by use of the time division multiplexing (TDM) technique. A stepper motor-based rotating system and a single-reflection spherical optical mirror were designed and adopted to realize and enhance multi-gas detection. Detailed measurements under static detection mode (without rotation) and dynamic mode (with rotation) were performed to study the performance of the sensor system for the three gas species. Effects of the motor rotating period on sensor performances were also investigated and a rotation speed of 0.4π rad/s was required to obtain a stable sensing performance, corresponding to a detection period of ~10 s to realize one round of detection. Based on an Allan deviation analysis, the 1σ detection limits under static operation are 2.96, 4.54 and 2.84 parts per million in volume (ppmv) for CO, CO₂ and CH₄, respectively and the 1σ detection limits under dynamic operations are 8.83, 8.69 and 10.29 ppmv for the three gas species, respectively. The reported sensor has potential applications in various fields requiring CO, CO₂ and CH₄ detection such as in coal mines.

Phosphorus species are the sum of naturally evolved phosphorus elements with diverse forms of existence and unique properties. The detection and analysis of the optical properties of unknown phosphorus species via direct or indirect strategies offers unique advantages in understanding the growth processes and existence characteristics of various chemicals and microorganisms in water environments. This review highlights recent advances and future trends in methods of detection of total phosphorus in water, including photoelectric strategies, spectroscopy techniques, and modeling algorithms. These methods effectively explore the dynamic changes of total phosphorus content in complex water environments to reveal important signals in water, which is of great guiding significance for achieving accurate detection of water quality and promoting social development. We also discuss some extended strategies for its measurement and prediction via rational design and cross-combination, which may help inspire future design of more accurate and intelligent detection models or systems. The strategies based on these types of total phosphorus detection methods provide a versatile platform for novel sensors and thereby show great potential in the development of future water quality detection applications.

Pole-climbing robots are increasingly needed to carry out high-risk tasks for human beings. A micro pole-climbing robot is designed in this article. A strategy of climbing pole is proposed, which has high precision in each stride. To enable the robot to sample the angle relative to the ground in real time, micro electro mechanical systems (MEMS) three-axis accelerometers are equipped on micro pole-climbing robot. Accelerometer measurements provide an absolute reference for the pitch-and-roll components of the estimated orientation, which are used as feedback input signal of proportional–integral–derivative algorithm. A supporting structure is installed at the joint of each gripper to assist the robot to clamp a pole. The support structure improves the load capacity of the robot. The maximum load of micro pole-climbing robot is 3.5 times its own weight. The climbing pole strategy includes the following sections: a Denavit–Hartenberg model is established and the inverse kinematic solution is analyzed; the flip locomotion is analyzed; and the parameters of K _P , K _I , and K _D in the proportional–integral–derivative control method are obtained according to the Ziegler–Nichols controller. The performance of pole climbing based on micro pole-climbing robot prototype was tested. By using this strategy of climbing pole, the self-continuous climbing with controllable stride is realized, and the angular velocity fluctuation of the five-bar mechanism driven by steering gear is reduced. The average time of a single step is 27 s, the maximum relative error of step distance is 4.6%, and the average relative error is 2.8%. These results confirm that the structure scheme and the strategy of climbing pole are feasible.

This paper proposes an Improved Quantum Particle Swarm Optimization algorithm based on Directional Maneuverability constrained by Isotropic Indexes (DMIIIQPSO). It can solve the problems of large inverse kinematics solution errors and the inability to solve singular configurations of 7-degree-freedom (DOF) redundant robotic arm. Firstly, we propose a new sports performance metric — Directional Maneuverability constrained by Isotropic Indexes (DMII). Introduce isotropic indicators to avoid singular configurations of the robotic arm. By combining the target attitude error function, a new objective function is obtained, and a robotic arm inverse kinematics mathematical model based on the combination of attitude error and DMII is constructed. Secondly, an improved QPSO algorithm was proposed. Introducing a three-segment and tangential piecewise Logistic chaotic maps can solve the problem of low accuracy in solving QPSO. The introduction of adaptive mutation criteria and improved particle position update mechanism has solved the problem of large inverse kinematics solution errors. Finally, the simulation experiment showed significant improvement in DMII-IQPSO. The search accuracy and search ability of the DMII-IQPSO algorithm have been greatly improved, and local optima can be avoided. The results show that the actual position reached by the robotic arm during operation matches the target point well.

The prediction of chemical oxygen demand (COD) by ultraviolet–visible absorption spectrum is a common method. Many researchers use the absorbance at the characteristic wavelength to establish COD prediction models. However, selecting the characteristic wavelength is a problem. In this paper, the extreme values of absorption spectrum change rate, was proposed as a new characteristic parameter to determine the characteristic wavelengths. On this basis, a novel hybrid strategy for detecting COD in surface water was proposed. We first proposed to combine the first derivative method with the permutation entropy method (FDPE) to determine the characteristic wavelengths. Then we used partial least square (PLS) to establish a COD prediction model. Experimental results demonstrated the linear correlation coefficient ($R^2$) of the FDPE_PLS was above 0.99 without turbidity interference. Secondly, a dual-wavelength method (DWM) was proposed to determine the turbidity values. The DWM used slopes of absorbance values at 400 nm and 600 nm to predict the turbidity values. Compared with the single-wavelength method, the DWM improves the measurement accuracy of turbidity. Finally, a new turbidity compensation method was proposed to compensate for the interference in the first derivative spectrum. After compensation, FDPE_PLS can predict COD concentrations accurately, whose $R^2$ was 0.99.

Surmounting obstacles during continuously climbing in a complex environment is an important issue for pole-climbing robots. An obstacle-surmounting strategy is presented for a pole-climbing robot. The force and moment applied on the pole-climbing robot in static status were analyzed, and the analysis of pole-climbing robot’s upward vertical climbing was conducted. The climbing execution has four steps: loosening the lower gripper, curling up, striding forward, and clamping the upper gripper. To obtain the information of obstacle crossing accurately, the obstacle-surmounting conditions were analyzed in detail. We modeled the striding linkage with thickness and obtained the Denavit–Hartenberg coordinates of each vertex. The model of the grippers with thickness was proposed and the Denavit–Hartenberg coordinates of each vertex of the grippers were obtained. Then single-step negotiating an obstacle and multistep negotiating an obstacle were proposed. Experiments were conducted to verify the effectiveness of the obstacle-surmounting strategy.