基于sigmoid滤波器的永磁轮毂电机自抗扰控制

相比燃油拖拉机,电动拖拉机具有节能高效、绿色清洁的优点。分布式驱动电动拖拉机结构简单、控制维度多,能进一步提高电动拖拉机的工作效率和作业精度。但是电机检测转速噪声导致轮毂电机速度波动严重,复杂路面及多种作业工况下进一步加剧了上述问题,严重降低了拖拉机的作业质量。针对上述问题,该研究提出一种基于sigmoid滤波器的线性自抗扰控制(linear active disturbance rejection control,LADRC)以提高轮毂电机的转速稳定性和抗扰动能力。该控制策略在传统LADRC的基础上引入sigmoid滤波器至扩张状态观测器(extended state observer,ESO),根据输入噪声信号误差变化改变滤波器带宽,以抑制观测误差中的中高频干扰信号,同时避免滤波器积分环节对轮毂电机速度跟踪快速性的影响,具有较快的收敛性。搭建试验平台对所提出控制策略进行试验验证,结果表明:与传统LADRC策略相比,本文所提控制策略在变速和变载工况下的转速脉动分别减小了32%和41.67%,iq电流脉动分别减小了6.25%和4.17%,可在快速、准确跟踪给定转速的同时,大幅提高轮毂电机驱动系统的噪声抑制性能,为复杂环境下电动拖拉机高精度作业提供技术参考。

基于AHP耦合Sigmoid函数的重载铁路黄土边坡风险分析

重载铁路具有大轴重、高密度、大运量的运输特点,黄土边坡路基段一直是重载铁路运营的高风险区段,现有风险评价方法尚无法满足其风险量化分析的需求。利用层次分析法AHP耦合Sigmoid函数的方法,围绕事故发生概率和损失两个方面对重载铁路黄土边坡工程展开风险定量评价。首先以边坡滑塌事故调研和稳定性控制理论为基础,明确黄土边坡的失稳影响因素,建立重载铁路黄土边坡稳定性评价模型和边坡失稳危害性评价模型;然后应用层次分析法建立黄土边坡稳定性评价模型指标权重,并提出各级影响因素的指标赋值方法;而后引入基于朴素贝叶斯理论的Sigmoid函数,构建边坡稳定服役概率、风险判断矩阵和黄土边坡的风险等级确定方法;最后以朔黄铁路某站高陡黄土边坡为工程背景,应用所得理论方法对其进行风险定量分析,计算得出该边坡失稳概率为0.64,造成经济损失约8611万元,隶属于高风险等级,并针对坡体几何特征、渗透能力、基岩特性等低分指标提出了具体的安全性提升措施建议。

ReLU激活函数深度网络的构造与逼近

研究ReLU激活函数深度网络的构造与逼近问题.以一个在[-1,1]上对x^(2)具有指数逼近阶的深度ReLU网络作为子网络,构造逼近任意n次多项式的深度网络,并给出其逼近误差的上界估计.借助一元正交切比雪夫多项式、张量积理论和函数逼近的方法,构造二元正交多项式和两个输入的深度网络,同时得到了对二元连续函数的逼近估计.

基于Sigmoid函数的非对称式S型曲线机械臂加减速控制方法

机械臂广泛应用于制造、装配、搬运、码垛等方面,对提高生产力起着重要作用。为减小机械臂在运动过程中的振动和冲击,提高机械臂轨迹执行效率,提出一种非对称式S型曲线加减速控制方法。该方法通过在双段Sigmoid函数中插入直线段,构成加加速度连续的运动学曲线。通过粒子群算法进行参数优化求解,无需反复确认每个时间段的存在性即可求出非对称约束下的曲线参数,并分别在关节空间和笛卡尔空间采用时间同步和位移同步方法使机械臂的运动轨迹更加协调自然。结果表明,相同条件下提出的方法比三角函数方法轨迹执行效率更高且加加速度仅为三角函数方法的55%。与梯形加加速度曲线相比,采用提出的方法规划的运动轨迹可减少35.7%的残余振动,验证了该方法的有效性。

一种Sigmoid为激活函数的高精度ANN电路的设计

提出了一款以Sigmoid为激活函数的人工神经网络(ANN)电路,实现对目标数据的分类,基于TSMC 180 nm CMOS工艺完成了电路设计、版图设计、仿真与流片测试,芯片面积为0.3375 mm^(2),1.8 V电源电压下电路功耗为216μW。3块芯片的测试结果显示,电路对目标数据的分类准确率为97.5%,误差在(-3.2%,3.27%)之间,平均误差为-1.51%。人工神经网络电路含有3个网络层,由15个Sigmoid激活函数神经元电路组成,两输入Sigmoid激活函数神经元电路由两个加权电路与一个Sigmoid激活函数电路组成。后仿真结果显示,在1.8 V电源电压下,神经元电路的功耗为8.02μW,最大噪声为√Hz,版图面积为0.001 mm^(2),最大相对误差为1.76%。

脉冲噪声下基于Sigmoid的LFM信号参数估计

由于脉冲噪声具有的短时大幅值特性,使得基于高斯假设的信号参数估计方法无法在脉冲噪声环境下有效估计参数。针对此问题,利用α稳定分布模拟随机脉冲噪声,提出了一种基于Sigmoid-CFRFT的LFM信号参数估计方法。首先,建立了一种自适应Sigmoid函数,证明了信号经过此非线性变换后,信号的2阶矩由无界变为有界,且信号的相位信息保持不变。其次,将变换后的信号进行离散时间CFRFT,建立了数学优化模型,并使用水循环算法搜索最优值点。最后,利用了非标准SαS分布噪声的修正方法,分析了标准和非标准分布下参数估计的性能。仿真结果说明,所提方法不仅可以有效抑制脉冲噪声对LFM信号分数谱特征的影响,而且能够实现低信噪比信号参数的高精度估计。相比于现有的基于非线性变换的参数估计方法,本文方法具有更好的精度,稳定性和噪声鲁棒性。

Adult sigmoid intussusception resembling rectal prolapse:A case report

BACKGROUND Rectal prolapse arises from benign etiology.When symptoms of internal intussusception mirror those of rectal prolapse,a misdiagnosis is possible,especially under limited clinical presentation.It is crucial to recognize and differentiate rectal prolapse from internal intussusception because the two diagnoses have different prognoses.Here,we describe a case of adult sigmoid intussusception presenting as rectal prolapse.CASE SUMMARY A 64-year-old woman with no known medical history visited a gastrointestinal outpatient department due to hard bloody stool defecation for 1 wk followed by constipation for 3 d.Colonoscopy revealed a huge polypoid ulcerated tumor at the sigmoid colon with lumen stenosis.The patient was admitted due to postprocedural dull abdominal pain.Due to failed colonoscopy reduction and stent insertion,the patient underwent sigmoid colon resection with primary end-to-end anastomosis,with the transverse colostomy pathological report showing adenocarcinoma,pT3N0M0.She recovered well from the operation and was discharged with regular outpatient clinic follow-up.CONCLUSION Presentation and manifestation of sigmoid intussusception may resemble that of rectal prolapse,necessitating careful observation due to distinct prognostic implications.

Comprehensive evaluation of rare case:From diagnosis to treatment of a sigmoid Schwannoma:A case report

BACKGROUND Schwannomas are uncommon tumors originating from Schwann cells,forming the neural sheath.They account for approximately 2%-6%of all mesenchymal tumors and are most commonly identified in peripheral nerve trunks,with rarity in the gastrointestinal tract.Among gastrointestinal locations,the stomach harbors the majority of nerve sheath tumors,while such occurrences in the sigmoid colon are exceptionally infrequent.CASE SUMMARY This study presented a clinical case involving a 60-year-old female patient who,during colonoscopy,was diagnosed with a submucosal lesion that was later identified as a nerve sheath tumor.The patient underwent surgical resection,and the diagnosis was confirmed through immunohistochemistry.This study highlighted an exceptionally uncommon occurrence of a nerve sheath tumor in the sigmoid colon,which was effectively managed within our department.Additionally,a comprehensive review of relevant studies was conducted.CONCLUSION The preoperative diagnosis of nerve sheath tumors poses challenges,as the definitive diagnosis still relies on pathology and immunohistochemistry.Although categorized as benign,these tumors have the potential to demonstrate malignant behavior.Consequently,the optimal treatment approach entails the complete surgical excision of the tumor,ensuring the absence of residual lesions at the margins.

Aggressive fibromatosis of the sigmoid colon:A case report

BACKGROUND Aggressive fibromatosis(AF),also known as desmoid tumor or desmoid-type fibromatosis,is a rare soft tissue neoplasm that can occur in almost any part of the body.Although it is a benign disease,AF is aggressive and infiltrative and has a high recurrence rate after surgery.Common sites for intra-abdominal AF are the small bowel mesentery,retroperitoneum,and pelvis.AF in the colon is extremely rare.CASE SUMMARY Here,we report the first case of sigmoid colon AF,which was accidentally discovered in a 27-year-old woman during laparoscopic myomectomy.Computed tomography confirmed a slightly enhanced mass in the sigmoid colon.Subsequent colonoscopy did not reveal a mass in the colonic lumen,but a suspected external compress was found in the sigmoid colon.Surgical disease involving a gastrointestinal stromal tumor was suspected.The patient underwent laparoscopic exploration,and sigmoidectomy with a negative margin was performed to excise the mass.Postoperative immunohistochemistry revealed that the mass was an AF.The patient recovered well and was recurrence-free at the 30-month follow-up without adjuvant therapy.CONCLUSION AF should be considered in the differential diagnosis of subepithelial colon masses.Radical resection alone can achieve good outcomes.

Unexpected right-sided sigmoid colon in laparoscopy: A case report and review of literature

BACKGROUND The presence of a right-sided sigmoid colon is a rare anatomical variation usually discovered incidentally during surgical interventions.This case report details an unexpected right-sided sigmoid colon identified during a laparoscopic appendectomy and examines the pertinent literature to explore its clinical importance.CASE SUMMARY A 71-year-old woman presented with acute appendicitis.A preoperative computed tomography(CT)scan showed peri-appendiceal inflammation but no significant anatomical abnormalities.During laparoscopic surgery,an unexpected finding was encountered:The sigmoid colon was situated on the right side and exhibited an abnormal relationship with the cecum and ascending colon.Postoperative pathological examination confirmed appendicitis with no additional pathological findings.The right-sided sigmoid colon anomaly was verified through intraoperative assessment and later re-evaluation with CT and colonographic imaging.The patient underwent a laparoscopic appendectomy and experienced a smooth postoperative recovery.CONCLUSION This case highlights the necessity of being attentive to anatomical variations during laparoscopic surgery,particularly when managing appendicitis.A review of the literature indicated that the occurrence of a right-sided sigmoid colon is infrequent and may be associated with anomalies in midgut rotation during embryonic development.Awareness of this variation can help prevent surgical complications and inform future clinical practice.

基于改进型sigmoid函数的混合储能系统SOC控制策略

介绍锂离子电池-超级电容混合储能系统的传统SOC控制策略,提出一种基于改进型sigmoid函数的SOC控制策略,并通过算例来展示混合储能模型的构建、仿真过程,分析验证基于改进型sigmoid函数的混合储能系统SOC控制策略的有效性。

Microscopic Structure of the Sigmoido-Jugular Junction in the Third-Trimester Fetus

Context and Justification: The sigmoido-jugular junction connects two structures of different compositions and has a complex organization. The sinusoidal portion of its endothelium contains muscle cells in adults. Is this the same presentation observed in fetuses? Objective: To describe the sigmoido-jugular junction in fetuses. Materials and Methods: Over a period of seven months, a histochemical and immunohistochemical study was conducted on 30 sigmoido-jugular junctions taken from 15 fetuses aged at least 32 weeks of gestation. These fetuses were obtained following expulsion due to intrauterine death, after informed consent from the parents. Results: Three portions can be identified: sigmoid, junctional, and jugular. Histochemical preparations revealed the existence of two constant layers and a third layer present only at the jugular level. From the inside out, the layers are as follows: 1) Inner Layer (Endothelium): This layer is clearer from the junction and reveals the presence of smooth muscle cells at the sigmoid level in immunohistochemistry. 2) Outer Layer: At the sigmoid and junctional levels, this layer consists of collagen fibers and becomes median at the jugular level, where it is composed of elastic and muscular collagen fibers. 3) Third Layer: Present only at the jugular level, this layer corresponds to the adventitia. Conclusion: The architecture of the sigmoido-jugular junction in fetuses, which is identical to that in adults, excludes the metaplastic hypothesis regarding endothelial smooth muscle cells in the sigmoid portion. Instead, it favors their role in regulating encephalic venous drainage.

利用Sigmoid函数所建隧道围岩全过程位移曲线的应用及效果验证

隧道围岩位移能够综合反映隧道施工过程中围岩稳定性及支护效果,但实际工程中掌子面前方围岩位移难以监测,导致难以得到围岩全过程位移曲线。为了获取隧道围岩全过程位移曲线,基于Sigmoid函数、遗传算法及数值计算方法,建立了隧道围岩全过程位移曲线,并验证了该曲线的预测效果。选取某公路隧道不同围岩级别工况下的典型位移监测数据,对所提出的预测方法进行验证,结果表明:基于Sigmoid函数的隧道围岩全过程位移曲线能够较为准确地预测围岩位移,预测精度和可靠性较高,适用于不同围岩级别及开挖方法,可为施工阶段围岩稳定性评价提供参考。

浅谈一种基于Sigmoid轨迹规划的相邻交叉耦合同步调平控制策略

随着武器装备的发展,雷达、天线、激光武器和火炮等军事设备都配有自动化调平系统,为了适应多变的战场环境,提高机动性能和战场生存能力,需尽可能地提高调平系统调平精度、调平效率,保证调平过程稳定。本文提出了一种基于Sigmoid轨迹规划的相邻交叉耦合同步调平控制策略,可以适用于多点调平场合。采用D-H坐标法建立平台位姿解算模型,得到各调平支腿所需位移。基于Sigmoid函数对位移调整过程进行规划,得到支腿位移和时间的序列关系。根据相邻交叉耦合同步控制策略,建立各支腿耦合关系,通过同步控制器实现各支腿按同步比例系数的同步调整。经SimMechanics动力学建模Simulink仿真结果如下:各支腿位移调整曲线平滑、调平效率高、调平误差小于3′,同步误差减小约55.6%,同步调整时间减小约44.4%。

一种用Sigmoid函数进行加权融合的图像去雾算法

为了解决图像去雾过程中在前景和天空区域过渡不平滑以及透射率融合不精确、恢复图像色彩不自然等问题,提出了一种用Sigmoid函数进行加权融合的图像去雾算法。该算法在R、G、B共3个通道上使用不同的衰减常数,并以Sigmoid作为权重函数将基于颜色衰减先验对天空区域的估计透射率和基于暗通道先验对前景区域的估计透射率进行融合,最后通过大气散射模型恢复出无雾图像。实验结果表明,该算法对包含有天空区域的雾图的去雾效果更优,复原后的图像清晰而且色彩自然,提升了图像的主观视觉效果,同时客观对比也表明了该算法的有效性和适用性。

基于改进Sigmoid函数的PMSM调速系统自抗扰控制

为实现永磁同步电机(PMSM)转速的快速、稳定控制,提出一种基于改进Sigmoid函数的自抗扰控制(ADRC)方法。首先,对Sigmoid函数进行了分析和改进,引入非线性因子;接着,利用改进Sigmoid函数替代传统非线性函数设计了PMSM调速系统的改进型微分跟踪器(TD)、改进型扩张状态观测器(ESO)和改进型非线性状态误差反馈(NLSEF)控制律,并借助李雅普诺夫(Lyapunov)函数证明了所设计的改进型ESO具有渐进稳定性;随后,证明改进型ADRC误差系统的渐进稳定性;最后,对该策略进行了仿真分析。结果表明:在PMSM调速系统中,改进型ADRC比传统ADRC和PI控制具有更好的动态性能和抗扰性能。

基于Sigmoid函数的机器人鲁棒滑模跟踪控制系统设计

为了保证机器人能够在保持稳定的情况下,按照规划轨迹执行工作任务,从硬件和软件两个方面,设计了基于Sigmoid函数的机器人鲁棒滑模跟踪控制系统。装设机器人传感器与状态观测器,改装机器人鲁棒滑模跟踪控制器,完成系统硬件设计;综合机器人结构、运动机理和动力机制3个方面,构建机器人数学模型;根据状态数据采集结果与规划轨迹之间的偏差,计算机器人跟踪控制量;依据滑模运动与切换方程,利用Sigmoid函数生成机器人鲁棒滑模控制律,将生成控制指令作用在机器人执行元件上,实现系统的鲁棒滑模跟踪控制功能;在系统测试与分析中,所设计控制系统的平均位置跟踪控制误差为0.93 mm,与设定轨迹目标基本重合,机器人姿态角跟踪控制误差为0.06 mm,具有较好的鲁棒滑模跟踪控制效果,能够有效提高机器人鲁棒滑模跟踪控制精度。

低照度下基于Sigmoid函数的改进同态滤波增强算法

针对低照度图像处理难度较大,信息含量少的问题,提出了一种基于Sigmoid函数的改进同态滤波低照度图像增强方法。该方法首先基于同态滤波增强方法的原理,并利用Sigmoid函数构造两个传递函数,对图像进行分频处理;然后将低通分量乘以相应的系数来控制图像的整体灰度;接着将高频、低频分量线性相加;最后输出增强后的图像。实验结果表明,该算法不仅优化了滤波器参数的调控问题,而且有效地提高了图像对比度,视觉效果更好,细节部分更清晰。

基于近似Kramers-Kronig关系的动态模量Sigmoidal模型力学演进研究

为了更好地描述沥青混合料的时间和温度依赖性,优选表征动态力学性质的黏弹力学模型,推广黏弹性动态力学设计方法。基于线性黏弹性Kramers-Kronig近似解析式,通过对存储模量Sigmoidal函数解析式求导后,得到损失模量解析式,称为SigmoidalⅡ类模型。应用黏弹性材料时-温等效原理,通过构造不同目标函数,建立了上述模型黏弹函数主曲线,并与SigmoidalⅠ-Ⅰ模型、SigmoidalⅠ-Ⅱ模型进行了对比分析。结果表明:3个模型均能应用时-温等效原理建立黏弹函数(动态模量和相位角)的主曲线,与AASHTO R 62-131规范对比,3个模型均提出了相位角主曲线解析式,目标函数构造时,黏弹参数的选择影响Sigmoidal模型的拟合效果。对比另外2个模型,SigmoidalⅡ模型仅采用一个黏弹参数(动态模量)构造目标函数即可建立所有黏弹参数主曲线及Cole-Cole曲线,且黏弹函数测试值与预测值吻合较好,其中,动态模量和相位角曲线的拟合优度均在0.95以上,说明该模型能更好地描述沥青混合料的动态黏弹参数。SigmoidalⅡ模型存储模量和损失模量(动态模量和相位角)共用一套模型参数,黏弹参数之间满足线性黏弹性因果关系且符合力学模型的要求。SigmoidalⅡ模型可为沥青混合料设计和沥青路面层状黏弹动力学计算提供新的参考。

Surgical treatment of pulsatile tinnitus related to the sigmoid sinus

Objective: Tinnitus-a common clinical symptom-can be categorized into pulsatile tinnitus(PT) and non-PT. Among these, PT is usually associated with sigmoid sinus symptoms, such as sigmoid sinus wall defect or diverticulum, for which various surgical treatments are available. We have discussed the clinical efficacy of surgery for sigmoid sinus-associated PT via the transmastoid approach in this study.Methods: We conducted a retrospective review of 4 patients who underwent surgery for sigmoid sinusassociated PT via the transmastoid approach at Nanjing Drum Tower Hospital from January to December2020. Of these, 2 patients had sigmoid sinus wall defect and 2 had sigmoid sinus diverticulum. Postoperative tinnitus grading and surgical efficacy were determined.Results: After surgery, PT dissolved in 3 patients, while tinnitus significantly decreased in 1 patient.During the follow-up period of 12-18 months, none of the 4 patients showed complications related to increased intracranial pressure or venous sinus thrombosis, and tinnitus symptoms disappeared in 3patients without recurrence, although 1 patient occasionally developed tinnitus. Postoperative thin-slice CTA of the temporal bone indicated that the sigmoid sinus bone wall defect or diverticulum was completely repaired with a thick soft tissue coverage.Conclusion: Surgical repair of sigmoid sinus-associated PT via the transmastoid approach deserves clinical promotion as it exhibited better efficiency while being relatively less invasive.