Evaluation of standing‐sitting support system with passive rotational seat mechanism in standing motion

Since a decrease in muscle mass of elderly people, the physical burden of them in standing‐sitting motion of a seat are increasing than young people. For this problem, several standing‐sitting support systems have been developed, and evaluations of these systems focusing on a reduction of physical load have been discussed. However, these evaluations are of support systems with an active actuators or of support systems when they use a handrail and a standing aid. Thus, an evaluation of a support system with only passive actuators has not been reported. In this paper, in standing motion with using a standing‐sitting support system with passive rotational seat mechanism which our group proposes, we objectively evaluate an effectiveness of the passive rotational seat mechanism by statistical analysis.     

磨削压力及速度对钢轨被动打磨性能的影响

以钢轨圆盘代替钢轨，设计一种模拟钢轨被动打磨方式的实验平台，研究被动磨削方式下磨削压力和磨削速度对磨削力、磨削温度、磨削效率及钢轨表面粗糙度的影响。实验结果表明: 在60～80 km/h范围内，随磨削速度增大，切向磨削力、表面粗糙度减小，磨削温度升高、磨削效率增大；在120～320 N范围内，随磨削压力增大，磨削温度升高、切向磨削力增大、磨削效率增大、表面质量下降。      

The optimization performance of cross‐linked sodium alginate polymer electrolyte bio‐membranes in passive direct methanol/ethanol fuel cells

Consumption of methanol and ethanol as a fuel in the passive direct fuel cells technologies is suitable and more useful for the portable application compared with hydrogen as a preliminary fuel due to the ease of management, including design of cell, transportation, and storage. However, the cost production of commercial membrane is still far from the acceptable commercialization stage. Based to our previous works, the low cost of cross‐linked sodium alginate (SA) polymer electrolyte bio‐membrane shown the virtuous chemical, mechanical, and thermal characterization as polymer electrolyte membrane in the direct methanol fuel cells (DMFCs). This study will further the investigation of cross‐linked SA polymer electrolyte bio‐membrane performance in the passive DMFCs and the passive direct ethanol fuel cells (DEFCs). The experimental study investigates the influence of the membrane thickness, loading of catalysts, temperature, type of fuel, and fuel concentration in order to achieve the optimal working operation performances. The passive DMFCs is improved from 1.45 up to 13.5 mW cm^?2 for the maximum peak of power density, which is obtained by using 0.16 mm as an optimum thick of SA bio‐membrane that shown the highest selectivity 6.31 10⁴ S s cm^?3, 4 mg cm^?2 of Pt‐Ru as an optimum of anode catalyst loading, 2 mg cm^?2 of Pt at the cathode, 2M of methanol as an optimum fuel concentration, and an optimum temperature at 90°C. Under the same conditions of cells, the passive DEFCs are shown to be 10.2 mW cm^?2 in the maximum peak of power density with 2M ethanol. Based on our knowledge, this is the first work that reports the optimization works of performance SA‐based membrane in the passive DMFCs via experimental studies of single cells and the primary performance of passive DEFCs using the SA‐based membrane as polymer electrolyte membrane.     

Adaptive neural network command filtered backstepping control of pure‐feedback systems in presence of full state constraints

An adaptive neural network (NN) command filtered backstepping control is proposed for the pure‐feedback system subjected to time‐varying output/stated constraints. By introducing a one‐to‐one nonlinear mapping, the obstacle caused by full stated constraints is conquered. The adaptive control law is constructed by command filtered backstepping technology and radial basis function NNs, where only one learning parameter needs to be updated online. The stability analysis via nonlinear small‐gain theorem shows that all the signals in closed‐loop system are semiglobal uniformly ultimately bounded. The simulation examples demonstrate the effectiveness of the proposed control scheme.     

Fuzzy approximation-based adaptive control of nonstrict feedback stochastic nonlinear systems with time-varying state constraints

This article develops an approximation-based fuzzy control scheme for nonstrict feedback stochastic nonlinear systems (NFSNS) with time-varying state constraints. The difficulty in constructing controller is how to conquer the algebraic loop problem caused by nonstrict feedback structure, as well as prevent the state constraints from violating. To dispose the time-varying state constraints, time-varying barrier Lyapunov function is incorporated into the backstepping design framework. The lumped uncertainties of NFSNS are approximated by the fuzzy logic systems. By virtue of fuzzy basis function, the algebraic loop problem is effectively handled. Theoretical analysis shows that the predefined state constraints are not violated and all signals of the closed-loop systems are bounded. Finally, simulation results substantiate the validity of the devised method.     

被动房整体气密性测试方法及应用

阐述了被动房整体气密性测试的必要性，列举了房屋整体气密性的常见测试方法，并重点介绍了压差法测试建筑气密性的过程和要点。     

Exponential Set-Point Stabilization of Underactuated Vehicles Moving in Three-Dimensional Space

This paper investigates the stabilization of underactuated vehicles moving in a three-dimensional vector space. The vehicle’s model is established on the matrix Lie group SE(3), which describes the configuration of rigid bodies globally and uniquely. We focus on the kinematic model of the underactuated vehicle, which features an underactuation form that has no sway and heave velocity. To compensate for the lack of these two velocities, we construct additional rotation matrices to generate a motion of rotation coupled with translation. Then, the state feedback is designed with the help of the logarithmic map, and we prove that the proposed control law can exponentially stabilize the underactuated vehicle to the identity group element with an almost global domain of attraction. Later, the presented control strategy is extended to set-point stabilization in the sense that the underactuated vehicle can be stabilized to an arbitrary desired configuration specified in advance. Finally, simulation examples are provided to verify the effectiveness of the stabilization controller.      

被动区土体加固技术在福州软土地区深基坑中的应用

本文针对被动区加固技术在福州软土地区的应用,结合福州市民服务中心工程的工程实际情况,通过分析研究被动区加固技术的作用原理,对水泥土搅拌工艺技术进行总结和改进。     

基于AMESim的比例方向阀与直驱式伺服阀故障特性分析

比例方向阀与直驱式电液伺服阀具有响应快、抗污性染性强等优点,广泛应用在各大工业领域。根据比例方向阀和直驱式伺服阀的结构和工作原理,利用AMESim软件搭建两种阀的仿真模型,仿真分析这两种阀在常见故障下的流量特性曲线,通过电液伺服阀性能检测平台将仿真与实验数据进行对比,验证了仿真模型的准确性。通过对这两种阀的分析,可为不同工况下液压系统设计中伺服阀的选择及伺服阀的故障维修提供参考。     

基于RBF最小参数学习法的正流量变量泵滑模自适应控制

为了提高正流量变量泵的性能,提出基于RBF最小参数学习法的正流量变量泵滑模自适应控制方法。分析正流量变量泵电液伺服系统的动力学特性,并进行系统辨识实验获得较为精确的系统数学函数模型;基于RBF最小参数学习法设计滑模控制器,在系统参数不确定性、摩擦力干扰和系统泄漏等非线性因素的情况下实现对目标流量的跟踪响应和自适应控制;最后利用MATLAB/Simulink对正流量变量泵的控制系统性能进行仿真实验,并和传统的PID控制器和模糊PID控制器进行比较。仿真实验结果验证了所设计控制方法的可行性和有效性。