Robotic distal ureterectomy with psoas hitch and ureteroneocystostomy:Surgical technique and outcomes

Use of the da Vinci■surgical robotic system has expanded to numerous upper and lower urinary tract procedures.We describe our surgical technique and perioperative outcome of robotic distal ureterectomy with psoas hitch and ureteroneocystostomy for distal ureteral pathologies.Eight patients with a median age of 69.5 years old underwent robotic distal ureterectomy with psoas hitch and ureteroneocystostomy between April 2009 and August 2014.The entirety of all cases was performed robotically by a single surgeon at a tertiary academic medical center.Median operative time was 285 min(range:210-360 min),estimated blood loss was 50 mL(range:50-75 mL)and median length of hospital stay was 2.5 days(range:1-6 days).There was one post-operative complication,a readmission for dehydration(Clavien Ⅰ).It suggests that robotic distal ureterectomy with psoas hitch and ureteroneocystostomy is a safe and effective minimally invasive alternative for patients with distal ureteral pathology.

Optimization of Specific Draft Requirement and Hitch Length for an Animal Drawn Sub-Soiler: A Case of Sandy Clay Loam Soils

This study aimed at optimizing tillage depth and hitching length for optimal draft requirement in sandy clay loam soils for animal drawn subsoiler. Field experiments were conducted to collect draft datasets using the MSI 7300 digital dynamometer communicating remotely with MSI-8000 RF data logger connected to a laptop through the serial port. To determine the numeric values of soil parameters pertinent to subsoiling, field experiments, laboratory tests and numerical analysis techniques were employed. For a specified speed, a combination of three hitch lengths of 2.5 m, 3.0 m and 3.5 m and three depths from 0 cm to 30 cm with a range of 10 cm interval was used. Soil bulk density was found to vary between 1.52 to 1.37 g/cm3 and 1.44 to 1.67 g/cm3 for Machakos and Kitui experimental plots respectively. Soil moisture content increased with an increase in depth ranging from 3.53% to 9.94% for Machakos site and from 4.15% to 9.61% for Kitui site. Soil shear strength parameters ranged between 21.71 and 29.6 kPa between depths of 0 - 20 cm and decreased to 28.07 kPa for depths beyond 20 cm at Machakos experimental plot;while for Kitui experimental plot, it ranged between 30.02 and 39.29 kPa between depths of 0 - 30 cm. A second-order quadratic expression of the form y = ax2 + bx + c was obtained for the relationship between specific draft and depth at given hitching length as well as specific draft against hitching length at a given depth. The optimal hitching length and tillage depth for Machakos experimental plot were obtained as 2.9 m (~3 m) and 16.5 cm respectively. In Kitui experimental site, the optimal hitching length was obtained as 2.9 m (~3 m) and the optimal tillage depth was 15.4 cm.

Design and performance analysis of indoor calibration device for the forcemeasuring system of the tractor three-point hitch

The real-time monitoring of the load in farming by the sensor installed on the tractor's three-point hitch can effectively improve the farming efficiency and force-position combined control,reduce the compaction risk of the wheel on the soil and reduce the fuel consumption in farming process.However,the measurement and quantification of the loads on the three-point hitch have some problems remaining unresolved:testing the accuracy and reliability of a load measuring system is hard when the tractor works in a field,the mathematical model of spatial forces usually lacks a practical and effective validation,and the calibration process of the measurement system is inconvenient and incomplete while easily causing a low accuracy.Specifically,this paper builds a new spatial-force mathematical model based on the geometry of a three-point hitch.To eliminate the discrepancy of the geometric model with the actual structure and to refine the mathematical model,a calibration process is conducted by developing a calibration bench,which is equipped with a data acquisition system and a multi-parameter monitoring interface.The three-point hitch installed on this calibration bench is subject to steady-state loading.The loading force,angle of the lower drawbar,and three-component forces(three shaft pin sensors’forces)of the three-point hitch are well measured.With applying for the measured data to calibrate the theoretical mathematic model eventually derives the resultant force from all the three-component forces,a dynamical loading bench was developed to test the calculated resultant force for the three-point hitch during the sinusoidal and randomly variant dynamical loadings tests.A hitch force measurement system is also developed to collect real-time data and calculate the resultant force of measured three-component forces through the calibrated mathematical model.The results of the dynamical loading tests show that the average relative error MRE=1.09%with an average force measurement time delay beingΔt=0.5 s,the root mean square error RMSE=59.3 N,and the coefficient of determination R2=0.9903.As observed,the shape and the trend of the generated resultant force curve are basically the dynamical loading force.The dynamical loading test proves the high efficacy and reliability of the proposed indoor calibration method for calculating the load based on the three-component forces as measured on the three-point hitch.Besides,the preliminary study of the proposed method on the hitch load provides great potential to improve the indoor six-component measurement and quantification of both the force and momentum acting on the three-point hitch.

Design and optimization of a new terrain-adaptive hitch mechanism for hilly tractors

In view of the problems of poor working quality and low efficiency caused by traditional hitch mechanisms,which cannot make farm implements adapt to hillside fields for terrain-adaptive working after leveling the body of hilly tractors,a new type of terrain-adaptive hitch mechanism was designed which can adjust the transverse posture of farm implements to meet the ploughing requirements of complicated terrain in hilly and mountainous areas.The mechanism was mainly composed of the original hitch device and the newly added rotating device.The kinematic model of each sub-mechanism was established,as well as the mathematical relation of significant performance indexes of the whole mechanism,such as lifting capacity,transverse inclination angle and tillage depth.Genetic algorithm was used to optimize the lifting performance of this hitch mechanism in Matlab,so that the minimum vertical lifting force at the center of gravity of farm implements increased by 14.1%,which met the requirements of national standards.Through ADAMS simulation calculation,it was found that different working slopes had a certain influence on the external load of each component,and terrain-adaptive hitch mechanism had little effect on the vibration characteristics of hilly tractors.The fatigue analysis and optimization design of the key component,rotating shaft,were carried out in ANSYS Workbench,and the mass of this part reduced by 64%.A real vehicle test platform was set up to test and verify the power lifting range and working slope range of terrain-adaptive hitch mechanism.The test results showed that the actual power lifting ranged in 185-857 mm,and the maximum error from the theoretical range was only 3.1%,while the actual working slope range was from–25.9°to+23.2°,and the maximum error from the theoretical range was only 4.5%.Therefore,the terrain-adaptive hitch mechanism can meet the requirements of power lifting performance,and simultaneously can adjust the transverse posture of farm implements for adapting to hillside fields of no less than 20°.

拖拉机三点悬挂电液加载系统研究与试验

三点悬挂系统是拖拉机关键工作系统之一。由于田间作业工况的复杂多变,拖拉机三点悬挂液压系统承受较大的随机载荷,容易发生零部件破坏与液压故障等问题,直接影响拖拉机安全及作业效率。基于以上问题,研发了拖拉机三点悬挂电液加载系统,并基于NI Compact-RIO开发了拖拉机加载平台测控仪与上位机测控软件,实现了信号采集与加载控制。利用ARMAX模型进行系统辨识,得到电液系统模型,并与MatLab传递函数辨识箱比较,平均绝对误差降低33.90%,均方误差降低87.36%,均方根误差降低64.45%;基于PID控制方法,上位机以20Hz加载频率将阶梯信号、正弦信号、田间三点悬挂牵引力载荷应用于加载系统进行复现,效果完全可以满足试验台的控制加载要求。试验结果表明:基于ARMAX模型的系统辨识及基于PID的控制方法结合三点悬挂电液加载系统,可将田间三点悬挂牵引力载荷加载复现,为基于田间动态载荷加载的拖拉机三点悬挂零部件与系统可靠性试验提供了平台和方法支撑。

基于发动机转速的拖拉机机组协同控制研究

拖拉机进行犁耕作业时受到土壤特性、道路坡度等不确定因素的影响,故针对拖拉机在作业中外部干扰的复杂与多变性,提出一种发动机转速-耕深协同控制的方法。基于AMESim与Simulink建立了拖拉机纵向动力学模型,考虑犁耕作业时土壤特性变化下农具牵引阻力的变化,通过对档位、油门位置、犁具耕深的控制实现了机组的综合自动化控制,获得了良好的动力性。仿真结果表明:在土壤阻力增加较小时,牵引阻力增加,发动机转速将降低,此时油门位置将增加以避免换挡;土壤阻力增加较大且油门位置为最大时,作业机具将小幅提升以避免转速急剧掉落;极限情况下,拖拉机将降挡以避免发动机熄火。台架试验表明:所提出的控制方法可实现通过减小耕深而保证发动机稳定运转的效果。

基于四杆机构拖拉机液压悬挂挂接装置设计与试验

液压悬挂系统是实现拖拉机与作业机具连接的关键部件,在拖拉机出厂前常采用人工挂接方式检测液压悬挂系统的承载性能,存在耗时长、效率低、存在安全隐患等缺陷。在不改变现有油缸加载检测装置的前提下,根据四杆运动机构设计了一种用于大中型拖拉机液压悬挂系统检测的挂接装置。结合四杆结构特点及拖拉机液压悬挂检测相关规定,分析了挂接装置的运动规律。基于四杆机构,设计了液压悬挂挂接装置,并对关键部件进行强度校核。在实验环境下,重复测试已研制液压悬挂挂接装置的挂接性能。试验表明:挂接装置的平均挂接时间为68.6 s、挂接成功率为96.7%,远低于人工挂接操作时间,并具有良好的挂接成功率。研制的液压悬挂挂接装置结构简单、性能可靠,降低拖拉机液压悬挂的检测强度、提高检测效率,为国内外拖拉机生产厂家设计一种用于拖拉机液压悬挂自动化检测系统提供依据。

Review of electro-hydraulic hitch system control method of automated tractors

The automatic and intelligent degree of tractor hitch system determines the operations quality,efficiency,tractor power output and energy consumption,and automatic control of electro-hydraulic hitch is one of the key technical problems in the realization of automated tractor.In this study,the adjustment methods and characteristics of electro-hydraulic hitch system were summarized.The development of electro-hydraulic hitch control technologies was elaborated and analyzed from both the electro-hydraulic control strategy and slip control strategy perspectives.The implementation methods and control characteristics were discussed.A new idea for the development of automated tractor was put forward that integrating cutting-edge technologies such as big data,fusion control and artificial intelligence.In addition,based on the precise and efficient control of electro-hydraulic hitch system,a high reliability of the control system of the tractor with intelligent application of the control algorithm was obtained.The results can provide a reference for the precise operation of automated tractors under the big data in agriculture.

离轴拖挂轮式移动机器人跟踪控制研究

针对离轴拖挂轮式移动机器人挂车的轨迹跟踪控制问题,基于拖车和挂车运动轨迹的相对曲率关系提出了一种动态跟踪方法。建立离轴拖挂轮式移动机器人的运动学模型和动力学模型。通过拖车和挂车位置几何关系给出了两车的速度关系,进而得到两车运动轨迹相对曲率之间的关系。基于曲率关系将挂车的运动任务转化为拖车的运动任务,并结合动态跟踪方法设计比例积分反馈控制器完成拖车的运动任务。最后通过模拟仿真实现了挂车精确的轨迹跟踪控制,仿真结果表明在所提控制器的作用下,挂车在拖车的拉拽下可精确地跟踪目标轨迹曲线。由于所使用的动态跟踪方法引入了目标轨迹曲线的相对曲率,极大地提高了跟踪的精确性。

绳索救援中普鲁士抓结安全性研究

为获得普鲁士抓结在极限受力情况下应用安全性的定量研究结果,了解普鲁士抓结失效时可能出现的情况,采用试验研究的方法,从主、辅绳直径差值、缠绕圈数等角度设置12个试验项目,通过拉力试验机对各试验项目逐一进行极限静拉实测,直至普鲁士抓结失效,得到普鲁士抓结失效的4种典型现象:短距滑移后绳圈断裂、多次短距滑移后绳圈断裂、短距滑移后主绳绳皮断裂和持续滑移。结果表明:主辅绳直径差越大、辅绳缠绕圈数越多时抓结的握持效果越佳;12.5 mm主绳与8 mm辅绳搭配且缠绕圈数为6圈时,是最佳使用组合,安全性最好。

电液提升控制阀技术特点分析

系统分析了当前主流电液提升控制阀的技术特点及控制原理,阐述了电比例控制阀与数字阀的技术区别,为后期控制阀的设计开发提供了建设性意见。从工况需求层面分析了电液提升控制阀技术路线的内在发展规律,作为电液提升系统的核心元件,电液提升阀的发展路线即为电液提升系统的发展趋势,为液压系统的设计选型及整机发展路径提供参考。

Magician Blaine Hitches Ride on London Eye Wheel

贵刊今年第8期曾经出现了London Eye。所谓“伦敦眼”,即位于英国伦敦的娱乐大转盘。本文的开头又出现了这个London Eye!真正让人叫绝的是,美国的玩命者将在英国伦敦泰晤士河旁被吊起的小“容器”中度过44天……

工作记忆中的语音回路与阅读理解的关系

语音回路是Baddeley和Hitch在1974年提出的工作记忆模型中的一个成分。由于语音回路本身的特点,人们联想到它可能和阅读理解这种复杂的认知活动有关系。为此,一些研究者从不同的角度,采用各种研究范式对这一问题进行了探讨。到目前为止,已有的大部分研究都支持语音回路对于阅读理解有作用,但也有少数研究不支持该观点。另外,对于语音回路影响阅读理解的机制问题,也存在着不一致的观点。

装配式建筑物塔式起重机的附着拉结措施

以往现浇混凝土结构施工期间的塔式起重机附着拉结方式,已不再满足装配式住宅建筑结构施工期间塔式起重机附着拉结的相关要求。以北京市某二类居住用地建设项目工程为基础,提出一种新的塔式起重机附着拉结方案,提出在塔式起重机附着的楼层设置H形钢柱、方钢斜撑,H形钢柱与楼板通过螺栓以及方钢斜撑进行连接,塔式起重机附着拉结在新增钢柱上,以解决塔式起重机与装配式建筑物的附着拉结问题。

中大拖电液提升控制系统分析

系统分析了当前主流电液提升系统的技术特点及控制原理,提出了国内主流电液提升控制系统提升改进的方向,为电液提升控制系统的设计提供了建设性意见。同时对其主要控制元件的技术发展思路进行了对比分析,为后期核心液压元件的开发提供了技术参考。

遗传搭车与方差分析在水稻定向选择群体的抗旱性位点分析中的初步应用

水稻抗旱性属于复杂性状,近年的遗传研究日益关注胁迫下的产量相关位点。选用来自同一抗旱性较好的供体亲本(BG300),具有两种遗传背景(IR64和特青)和两种选择条件(低地和旱地)的4个水稻高代回交(BC2)抗旱性定向选择导入系群体。通过SSR分子标记,检测群体中供体等位基因的导入频率,分析了选择条件和遗传背景对供体等位基因导入频率的影响。在此基础上,利用基于遗传搭车原理的卡方检验对等位基因导入频率的偏离进行检测,同时结合表型-基因型方差分析(ANOVA)的方法,对上述群体进行了和抗旱性相关位点的QTL分析。共检测到显著位点24个,其中卡方检验发现20个,方差分析检测到8个。有4个被这两种方法都检测到,很可能是与胁迫下的产量直接相关的位点。同时也对非胁迫下的产量位点进行了检测,发现上述抗旱性位点与非胁迫下产量的关系不大。还就选择条件和遗传背景的效应等对目标性状QTL定位的影响进行了讨论。研究结果将为进一步的水稻抗旱性分子育种研究提供有用的信息和材料。

拖拉机电液悬挂系统模糊PID自适应控制方法

将模糊PID自适应控制方法应用到拖拉机电液悬挂系统控制中。根据系统特性,设计了模糊PID自适应控制器,建立了电液悬挂系统模型,并与普通PID控制方法进行了牵引力控制、位置控制性能仿真分析。搭建了试验台对电液悬挂系统进行田间试验。试验结果表明,采用模糊PID自适应控制以后,电液悬挂系统设定耕深由0.1 m阶跃至0.3 m时,系统过渡过程时间为4 s,无超调量;设定牵引力由3 kN阶跃至7 kN时,系统过渡过程时间为5 s,系统超调量为25%。

基于推杆电动机的拖拉机液压悬挂控制系统

设计的拖拉机液压悬挂自动控制系统包括推杆电动机、传动机构和控制单元ECU等。控制单元ECU实时接收上位机决策控制指令,控制推杆电动机驱动拖拉机液压悬挂的提升器,调整作业机具至适宜的位置。设计了双阈值斜坡启动和反馈PI算法相结合的PWM电动机控制方法,启动阶段以前馈斜坡输入控制为主,使推杆电动机可以平稳且快速地启动;主体运行阶段以PI反馈控制为主,以提高控制速度和精度。采用C语言实现整个控制系统编程,包括电动机反馈信号的AD转换采集、电动机的PID控制、上下位机的CAN通讯以及串口通讯等内容。试验测试结果表明,前馈斜坡启动方式可以较好地避免电动机启动时的瞬间冲击电流;当死区阈值设置为10(AD)时,最大误差范围为±11(AD),体现在推杆电动机上的行程误差为±0.26 mm,满足拖拉机液压悬挂系统的自动操纵控制要求。

拖拉机耕深模糊自动控制方法与试验研究

研究了拖拉机电控液压悬挂系统耕深自动控制方法,提出了一种基于模糊控制的电控液压悬挂系统耕深自动控制方法和综合度系数的概念,设计了耕深模糊控制器,并利用综合度系数将力位综合调节转化为对耕深的模糊控制。试验研究了阻力在不同综合度系数下对耕深的影响,试验结果表明:耕深从0到20 cm的响应时间低于1.7 s,当综合度系数分别为0.7、0.5和0.3时,耕深受阻力的影响分别减少了3.2、3.8和5.6 cm,过渡时间分别为0.79、0.93和1.21 s,该控制方法能够满足耕深自动控制的要求。论文提出的基于模糊控制的力位综合调节方法,利用综合度系数,以耕深和阻力为控制参数,可以实现耕深的双参数控制,为拖拉机电控液压悬挂系统耕深进行力位综合控制提供理论依据。