Ergonomics study on the handle length and lift angle for the culinary spatula

The culinary spatula (turning shovel) is one of the most common cooking tools used in the kitchen in Asia. However, the culinary spatula has seldom been ergonomically investigated. When a person uses a spatula to cook food, the operations involve repetitive bent-wrist motions, such as dorsiflexion, palmary flexion, and radial and ulnar deviations. These movements may cause cumulative trauma disorders in the upper extremities, and in particular carpal tunnel syndrome. A poorly designed culinary spatula will be ergonomically inefficient and cause injury to the hand and wrist. The purpose of this study was to investigate the effects of spatula handle length and lift angle on food-frying, food-turning, and food-shoveling performance. Eight female subjects were tested using 16 different culinary spatulas, with four different handle lengths (20, 25, 30 and 35 cm) and four different lift angles (15 degrees, 25 degrees, 35 degrees and 45 ). The criterion measures included cooking performance, and rating of perceived exertion. The subjects ranked their preference after all of the tasks in the tests were completed. The results showed that: (1) The handle length had a significant influence on the cooking performance, and rating of perceived exertion. The optimal handle lengths for frying food, turning food, and shoveling food were 20, 25 and 25 cm, respectively. (2) The lift angle significantly affected the cooking performance, and rating of perceived exertion. The optimal lift angles for frying food, turning food, and shoveling food were 15 degrees, 15 degrees and 25 degrees, respectively. (3) Both the handle length and lift angle had significant effects on subjective preference. For the handle length, the 20 cm length was the best. For the lift angle, the 25 angle was the best. (4) In general, a spatula with a 20 cm handle length and 25 degrees lift angle was the best. A spatula with a 25 cm handle length and 15 lift angle was the second most preferred. (5) However, to prevent subjects from touching the edge of a hot pan, a spatula with a 25 cm handle length and 25 lift angle is suggested.     

电铲履带系统Adams ATV动态仿真

针对重型履带系统复杂的车辆 地面力学问题，使用Adams ATV模块建立电铲整机模型，准确计算在软地面爬坡、转弯和越障等工况下履带系统的驱动力矩和支重轮受力。爬坡工况下履带系统驱动力矩仿真结果与理论值基本一致，转弯工况下驱动力矩理论值与仿真结果的相对误差在2.5%～26.2%区间；原地转弯所需驱动力矩与12.5°坡角爬坡所需驱动力矩接近。在硬地面越障时，支重轮受力最大值占整机总重力的41.8%。与实际使用值对比结果表明，仿真结果和理论计算值可作为方案设计的参考，且理论计算值偏于保守；各工况计算结果可为动力配置和后继强度设计提供依据。     

Robust outdoor stereo vision SLAM for heavy machine rotation sensing

The paper presents a robust outdoor stereo vision simultaneous localization and mapping (SLAM) algorithm. It estimates camera pose reliably in outdoor environments with directional sunlight illumination causing shadows and non-uniform scene lighting. The algorithm has been developed to measure a mining rope shovel’s rotation angle about its vertical axis (“swing” axis). A stereo camera is mounted externally to the shovel house (upper revolvable portion of the shovel), with a clear view of the shovel’s lower carbody. As the shovel house swings, the camera revolves with the shovel house in a planar circular orbit, seeing differing views of the carbody top. During the swing, the SLAM algorithm builds a map of observed 3D features on the carbody and simultaneously using these landmarks to estimate the camera position. This estimated camera position is then used to compute the shovel swing angle. Two novel techniques are employed to improve the SLAM algorithm’s robustness in outdoor environments. First, a “Locally Maximal” feature selection technique for Harris corners is used to select features more consistently in non-uniformly illuminated scenes. Another novel technique is the use of 3D “Feature Clusters” as SLAM landmarks rather than individual single features. The Feature Cluster landmarks improve the robustness of the landmark matching and allow significant reduction of the SLAM filter computational cost. This approach of estimating the shovel swing angle has a maximum error of ±1° upon SLAM map convergence. Results demonstrate the improvements of using the novel techniques compared to previous methods.     

Influence of snow shovel shaft configuration on lumbosacral biomechanics during a load-lifting task

Lower-back injury from snow shovelling may be related to excessive joint loading. Bent-shaft snow shovels are commonly available for purchase; however, their influence on lower back-joint loading is currently not known. Therefore, the purpose of this study was to compare L5/S1 extension angular impulses between a bent-shaft and a standard straight-shaft snow shovel. Eight healthy subjects participated in this study. Each completed a simulated snow-lifting task in a biomechanics laboratory with each shovel design. A standard motion analysis procedure was used to determine L5/S1 angular impulses during each trial, as well as peak L5/S1 extension moments and peak upper body flexion angle. Paired-samples t-tests (α = 0.05) were used to compare variables between shovel designs. Correlation was used to determine the relationship between peak flexion and peak moments. Results of this study show that the bent-shaft snow shovel reduced L5/S1 extension angular impulses by 16.5% (p = 0.022), decreased peak moments by 11.8% (p = 0.044), and peak flexion by 13.0% (p = 0.002) compared to the straight-shaft shovel. Peak L5/S1 extension moment magnitude was correlated with peak upper body flexion angle (r = 0.70). Based on these results, it is concluded that the bent-shaft snow shovel can likely reduce lower-back joint loading during snow shovelling, and thus may have a role in snow shovelling injury prevention.     

一种新的智能避障转向控制方法

针对智能探测车的转向系统建立精确的数学模型十分困难,且其航向受诸多因素干扰问题,研究了预测控制中的动态矩阵法,提出了一种新的智能探测车转向机构模型。该方法用障碍物的方向和距离偏差作为参数,在预测控制算法中采用动态矩阵控制,输出前轮转向角。再将转向角预测量与实际转向角之和作为反馈,对转向角变化趋势做出预测。通过仿真验证了在不同纵向速度下,加入相同干扰时的系统响应。结果表明：该算法在智能探测车障碍物避让控制中,对外界环境的干扰具有较强的鲁棒性,能够满足智能探测车转向控制要求。     

Investigating the influence of route turning angle on compliance behaviors and evacuation performance in a virtual-reality-based experiment

Route turning is one of the most essential and ubiquitous physical features in the complex building environment. Under the influence of route turning, evacuees’ approaching perspective to an emergency sign could vary, affecting their information perception and behavioral compliance during the evacuation. Although conventional simulation methods assess the effectiveness of the emergency sign in the visible region, they fail to consider evacuees’ wayfinding behaviors and interaction with the emergency sign. It remains unclear whether the route turning angle affects evacuees’ compliance for detecting and responding to the emergency sign. To investigate such an influence, a virtual-reality-based method for assessing human evacuation behaviors in building fire evacuations was proposed. In this study, two evacuation routes with different turning angles in a shopping mall were created and implemented in a virtual-reality environment, and 67 subjects participated in the immersive virtual-reality-based experiment. All participants took the two routes to find the nearest exit for evacuation in a fire event, aiming to evaluate the effect of the route turning angle on the evacuation process. The participants were asked to complete a questionnaire at the end of the experiment. Next, statistical analyses were conducted on evacuation results, information perception, and evacuation performance of the participants. The results indicated the route turning angle significantly affected participants' behavioral compliance with emergency signs. The results also suggested the route turning angle was influential on participants’ information perception and evacuation performance. Besides, a significant effect on rotation change, wayfinding pause, and speed deviation were observed. This study validates the effectiveness of investigating evacuees’ interaction with emergency signs using virtual-reality technology and has potential implications for complex building path planning and evacuation simulation modeling.     

Investigations pertaining to continuous and intermittent cranking motion

Crank radius, frictional torque, plane angle and direction of turning (viz. clockwise and anti-clockwise) are known to affect the cranking time. Adequate prediction models incorporating these factors are not available to the designers of man-machine systems. Consequently a set of experiments were conducted using three different radii, three levels of torque, three different plane angles, and two turning directions for continuous as well as intermittent cranking. Five male and five female right handed subjects performed these experiments. The results indicated the superiority of a clockwise turning direction. The effect of radius, torque, and plane angle were found to be significant. Furthermore, prediction models for the turning rate for continuous and intermittent cranking were developed.     

Kinematic evaluation of two snow-shovel designs

The objective of this study was to determine how different shovel designs affect trunk motion during snow shoveling. A shovel having a straight shaft and a shovel having a bent shaft were evaluated across three levels of task asymmetry. The primary dependent variables were measures of lumbar kinematics in three directions with respect to the spine (sagittal, rotational, and frontal) recorded with a lumbar motion monitor. Ratings of perceived discomfort and measures of heart rate were also collected. In a laboratory experiment, 12 participants were required to stimulate snow shoveling in three different directions with each shovel. Results showed that the bent shovel significantly reduced the lumbar velocity and acceleration in the sagittal plane without affecting motion in the rotational or frontal planes. Most sagittal and rotational motion parameters increased significantly as throwing direction became more asymmetric. The discomfort ratings indicated that the low back, arms, and wrist were the body regions most severely affected by the task, with some evidence of differences between the two shovel designs.

Relevance to industry

The use of a bent-handled shovel will reduce lumbar sagittal flexion without increasing side bending and twisting during snow-shoveling work. However, the use of multiple shovel designs during snow removal may be needed to reduce discomfort of the upper extremities.     

A comparative study of two shovel designs

In the present study a modified shovel design with two perpendicular shafts is presented. This modified, two-shaft shovel was compared with a regular shovel. The modified shovel was evaluated and tested in a controlled laboratory environment using surface electromyography recorded from the lumbar paraspinal muscles. The new shovel design was also tested in a field study using ratings of perceived exertion. The results indicate that there was a significant reduction in EMG values of the lumbar paraspinal muscles and a consistent reduction in perceived exertion ratings while the modified shovel was being used for removing dirt in digging trenches up to 90 cm in depth.     

Physiological and subjective measures of workload when shovelling with a conventional and two-handled (‘levered’) shovel

Previous studies have suggested that the two-handled (levered) shovel is advantageous over the conventional spade from a biomechanical point of view. The aim of this experiment was to determine whether less energy was consumed while shovelling a load of sand with this shovel compared to a conventional tool. Accordingly, an experiment was designed in which subjects (n = 10) shovelled 1815 kg sand under laboratory conditions using either a conventional or a levered shovel. Heart rate and oxygen consumption were measured continuously during the trial and subjective data on perceived exertion, general fatigue and body discomfort were recorded after the trial. Although total energy expenditure was similar under both conditions (120±20 and 125±25 kcal; conventional versus two-handled spade), average heart rate was 4% higher when the two-handled &lt;. shovel was used (p<0 05). In addition, the mass of sand per scoop was 4% less &lt;. with the two-handled shovel (p<0 05). In conclusion, subjects used similar energy expenditure to shovel 1815 kg sand with the conventional shovel and the twohandled tool despite lower mass of sand per scoop with the latter. This can be explained by the fact that the increased mass of the additional handle compensated for the lower mass of sand per scoop. The higher average heart rate while shovelling with the two-handled shovel can be explained by the more erect posture.     

A study of flows in tangentially crossing micro-channels

In the present study, flow fields in the three-dimensional, tangentially crossing micro-channels were studied. The effect of the relevant geometrical parameters such as the aspect ratio, contact surface area, surface to volume factor, flow rate and cross angle on the flow turning was reported. When the geometries and the flow conditions of the two crossing channels were the same, the fraction of turning flow was found to be dependent on the aspect ratio of the channel as reported previously in the literature. However, if the configuration and flow conditions of the two channels were different, the results need to be clarified. A parameter of non-dimensionalized surface to volume ratio was devised to characterize the flow turning. And the parameter was tested against its validity using numerical simulation and the available experimental data. The experiments on the crossing angle were conducted to show that larger angle in general yielded higher turning flow ratio. The results are expected to be useful in the passive control of flow in micro-fluidic devices among others.     

基于阿克曼原理的车式移动机器人运动学建模

基于阿克曼原理的轮式移动机器人运动学模型对于无人驾驶车辆的研究有着重要的意义.对轮式移动机器人的运动学特性进行了分析,建立了不考虑滑行、刹车等的轮式移动机器人的运动学模型.对该运动学模型引入了阿克曼约束,给出了描述机器人运动状态的转向角、航向角和转弯半径等物理量的数学公式.最后对该运动学模型进行仿真实验,验证了所建立的运动学模型的正确性,为进一步研究轮式移动机器人提供了理论分析的基础.     

连续小直线段高速高精插补中的动力学约束条件

针对连续小直线段高速高精插补算法中起始点和终止点的速度规划，建立了包含机床加减速性能、转接处误差控制、最大加速度以及机床负载功率等的速度约束条件．通过仿真实验得出：当连续小直线段间拐角较小时，机床加减速性能是影响加工效率和表面精度的最主要因素；当拐角增大到一定程度时，误差的限制成为约束速度提高的主要矛盾；当拐角较大时，机床的最大驱动力矩起到主要作用．     

Research on unmanned electric shovel autonomous driving path tracking control based on improved pure tracking and fuzzy control

This paper proposes a path tracking control method combining pure tracking algorithms and self-adaptive fuzzy control for autonomous driving of an unmanned electric shovel. An improved pure tracking controller was designed based on the kinematic model of heavy crawler taking both the value of deviation and its variation as inputs with the crawler speed on each side as output. The proposed controller and MPC algorithm were simulated using MATLAB for comparison. The results show that the proposed controller has more anthropomorphic characteristics than the MPC method. To verify the actual control effect of the controller, experiments were carried out using a prototype electric shovel for different working conditions. The experimental results proved that the controller is able to meet the control requirements for unmanned electric shovel path tracking.     

移动机器人的在线实时定位研究

对推算定位法进行了研究,提出了一种改进方案.通过对移动机器人运动轨迹与状态的分析,导出了一类移动机器人的基于轨迹的运动学新模型.利用移动机器人三个轮子的里程信息和导向轮的转角信息,通过信息模糊融合获得转弯半径和转角,再利用运动学模型获得机器人的位置和方向.将这种改进的推算定位法与主动灯塔法相结合,提出了一种用于室内移动机器人的定位方法.仿真结果表明,该方法具有实时性好、精度高、成本低、鲁棒性好等特点,并适用于不平整地面.     

避险车道驶入角计算方法评价

避险车道驶入角取值直接影响失控车辆能否安全驶入避险车道。基于车辆动力学仿真采用极限侧向加速度参数评价避险车道驶入角计算方法。首先,通过失控车辆稳定性分析确定车辆极限转弯半径;其次,采用三种驶入角的计算方法分别计算三种车速对应的避险车道驶入角;最后,基于车辆动力学仿真软件TruckSim,分别建立失控车辆和避险车道仿真模型,以极限侧向加速度作为评价指标设计并完成3组车辆稳定性仿真。仿真结果表明:方法二比方法三合理。对于方法二,进一步分析驶入角与主线转弯半径的关系,结果也表明方法二比方法三合理;继续采用极限侧向加速度作为评价指标并进行仿真,优化方法二的驶入角范围并与其它研究对比,结果表明了方法二优化结果的正确性。     

Concept and model experiments on automatic shoveling of rocks from the rock piles

This paper is concerned with the robotics of the shovel dozer. One methodology to distinguish between the rock pile and the huge rock was proposed in this study. The concept of this method is based on the difference of the time history of the force acting on the lift arms of the shovel dozer model. By using this model, two kinds of experiment on shoveling the rocks were carried out with changing the RPM of the motor. It was confirmed that stable shoveling was conducted.     

基于序列图像处理法的机器鱼转向机动性能研究

基于序列图像处理法，对机器鱼的转向性能进行了初步研究．利用高速摄像机记录机器鱼运动过程， 对游动序列图像进行处理，提取机器鱼体干曲线，获取机器鱼转向运动中角度、角速度、角加速度的动态特性．根 据实验结果，给出了机器鱼C 形转向运动的3 个阶段的运动特征，并对理论值和实验测定值之间的差异进行分析． 同时，对静止和运动两种C 形转向运动进行比较，分析了影响C 形转向效果的因素：初始动能以及保持阶段角度大 小，在此基础上，给出了提高机器鱼转向性能的方法．     

基于转角约束的改进蚁群优化算法路径规划

针对传统蚁群优化（ACO）算法搜索路径时易陷入局部最优、路径过长、转弯角度过大等问题,提出一种基于转弯角度约束的改进ACO算法。首先,增加起始点与目标点之间区域的初始信息素浓度,以避免初期盲目搜索;然后,在启发函数中加入A^*算法的估价函数和转弯角度因子,以便在下一步选择路径长度和转角次数综合最优的节点;最后,在信息素更新部分引入狼群算法的分配原则,来加强优质种群的影响力,同时借鉴最大最小蚁群（MMAS）算法进行信息素浓度的限制,从而避免算法陷入局部最优。Matlab仿真结果表明,改进算法与传统ACO算法相比,规划出的路径长度缩短了13.7%,转弯次数减小了64.3%,累计转弯角度减少了76.7%。实验结果表明,所提改进算法能有效解决全局路径规划问题,避免了移动机器人过多的能耗损失。     

Modeling Truck–Shovel Systems as Closed Queueing Network with Multiple Job Classes

In this paper an analytical method is proposed to model the truck–shovel system as a closed queueing network with multiple job classes. This approach would provide the capability of estimating system performance measures (mine throughput, mean number of trucks, mean waiting time etc.) for planning purposes when the truck fleet is not necessarily composed of identical trucks. A computational study is presented to show how choosing different types of trucks affect the production level in a truck–shovel system. Mean Value Analysis (MVA) approach is used to compute all performance measures of the truck–shovel system.