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1.
It has been known from empirical equations that soil strength can be determined if wheel sinkage and slip of a vehicle can be measured on a soil surface. In this study, field data of wheel sinkage and slip were collected from two platform tractors of different sizes on gravely sandy and sandy loam soils. Using an empirical equation, the rating cone index was determined using the measured wheel sinkage and slip data. The data demonstrated that the same rating cone index can be obtained although the measuring platforms are different. It was also noted that the rating cone index can be estimated in real time by measuring the sinkage and slippage of a driving wheel. 相似文献
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In this paper, performances of two model-free control systems including Fuzzy Logic Control (FLC) and Neural Predictive Control (NPC) on tracking performance of wheel-slip in Anti-lock Braking System (ABS) are compared. As an accurate and control oriented model, a half vehicle model is developed to generate extensive simulation data of the braking system. Brake system identification is preformed through a Perceptron neural networks model of brake system which is trained with offline data by Gradient Descent Back Propagation (GDBP) algorithm. In order to reduce the time cost of the calculations and improving the robustness of closed loop control system, an online Perceptron neural network adaptively generates the optimum control actions. By a comparative simulation analysis it is shown that the NPC system has a better tracking performance, shorter stopping time and distance than the FLC controllers. The robustness of the proposed control systems are evaluated under ±25 % uncertainty. It is shown that the NPC system is more robust against both exogenous disturbances and modeling uncertainties than the FLC system. 相似文献
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This study was conducted to investigate the effect of circumferential angle, lug spacing and wheel slip on forces produced by a cage wheel. Experiments were conducted in a laboratory soil bin having Bangkok Clay soil with 51% (d.b.) soil moisture content. Six ring-type loadcells were used to measure the soil horizontal, vertical and transverse reactions on the cage wheel lugs. The circumferential angle was varied from 0, 15, 30 to 45°. The lug spacing and wheel slip were varied from 20, 30 to 40° and 20, 35 to 50% respectively. All the force measurements were done at a constant 7 cm sinkage. The results showed that increasing circumferntial angle up to 45° can reduce variation in lug wheel forces, at the same time it had little effect on the mean pull and lift values. The side force was affected by the changes of circumferential angle. The 20° lug spacing not only gave the minimum variations but also maximum mean lug forces. The highest lug wheel forces occurred at 35% wheel slip. 相似文献
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《Journal of Terramechanics》1992,29(6):599-604
The Slip and Drift Model (SDM) of a wheel with tyre, introduced in 1969, has brought the formally correct fundamental solution to the two-dimensional problem of a wheel motion: longitudinal force-lateral force-slip-drift (slip angle) relationship. It has taken into account the tyre elasticity and the specifics of soil behaviour. In some recent attempts to compile a modified model, the SDM was either ignored or presented inadequately. The analysis of two such attempts from 1981 and 1987 has revealed that their kinematic formulae reproduce the basic formulae of the SDM and that their static equilibrium formulae, as far as they are based on the resolution of the soil shear stress into x, y components, are not satisfactory as a matter of principle. 相似文献
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The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy recovery.There remain technical challenges mainly because of the nonlinear,uncertain,and varying features of wheel-rail contact conditions.This research analyzes the torque transmitting behavior during regenerative braking,and proposes a novel methodology to detect the wheel-rail adhesion stability.Then,applications to the wheel slip prevention during braking are investigated,and the optimal slip ratio control scheme is proposed,which is based on a novel optimal reference generation of the slip ratio and a robust sliding mode control.The proposed methodology achieves the optimal braking performancewithoutthewheel-railcontactinformation.Numerical simulation results for uncertain slippery rails verify the effectiveness of the proposed methodology. 相似文献
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A microcontroller-based embedded digital display and warning system was developed for measuring wheel slippage, velocity ratio, PTO torque, and draft requirement of active tillage machinery. The hardware system included magnetic pickup sensor for measuring the engine speed, load cells and amplifiers to measure and amplify the sensing unit signals of the draft, proximity sensors for wheel slip, and PTO torque transducer for measuring the torque requirement. It was provided with buzzers and LEDs to warn the operator, whenever slip and velocity ratio were not in the desired range based on the algorithm, for maximum fuel efficiency and tractive performance. It measured slippage, velocity ratio, torque and draft with a maximum absolute variation of 12.90%, 7.92%, 8.99% and 11.57%, respectively. The developed system can be easily adaptable to any combination of tractor and tillage implements, and guide the operator for better soil tilth with lesser energy input. 相似文献
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A hall sensor based simple technique was introduced to measure wheel slip and a microcontroller based embedded digital system was developed to display wheel slip data and warn the operator with audible and visible warnings if the optimum range is exceeds. Hall sensor slip measurement system was validated in controlled soil bin condition, tar macadam surface and actual field condition and compared with the commercial radar sensor. The developed system is simple in construction and can be mounted to any make and model of agricultural tractors by entering the appropriate rolling radius via the computer interface. Field trials were conducted to measure wheel slip and fuel consumption on farm use with and without activation of slip indicator; it was observed that, the amount of fuel saving during various agricultural operation was up 1.3 l/h. 相似文献
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Koichiro Fukami Masami Ueno Koichi Hashiguchi Takashi Okayasu 《Journal of Terramechanics》2006,43(3):287-301
Soil–wheel interaction especially soil deformation caused by the wheel motion was investigated experimentally using a sophisticated soil bin test apparatus and an on-line measurement system for soil displacement. Based on these test results, characteristics of soil deformation were summarized focusing on the behavior and distribution of displacement increment vectors. Mathematical models were examined in order to describe the displacements of soil particles. Properties of the displacement loci are described. The magnitude of the displacement increment vector, its horizontal and vertical components are discussed, and characteristics of these distributions with respect to the relative horizontal distance from the vertical centerline of the wheel to the target point are clarified. Shapes of these distribution curves were closely similar to those of the derivatives of a Gaussian function. A distribution curve of the horizontal displacement increment had two peaks and that of the vertical one had three peaks. Based on the results, mathematical models for those displacement increments were proposed by employing a Gaussian function through multiplication of a linear function and a quadratic function. Predicted distributions and displacement loci of the models agreed with high accuracy to the measured values. The mathematical models were extended taking into consideration the wheel slip. The predicted distributions according to test conditions agreed very well to the measured results. 相似文献
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In forest harvesting, terrain trafficability is the key parameter needed for route planning. Advance knowledge of the soil bearing capacity is crucial for heavy machinery operations. Especially peatland areas can cause severe problems for harvesting operations and can result in increased costs. In addition to avoiding potential damage to the soil, route planning must also take into consideration the root damage to the remaining trees. In this paper we study the predictability of boreal soil load bearing capacity by using remote sensing data and field measurement data. We conduct our research by using both linear and nonlinear methods of machine learning. With the best prediction method, ridge regression, the results are promising with a C-index value higher than 0.68 up to 200 m prediction range from the closest point with known bearing capacity, the baseline value being 0.5. The load bearing classification of the soil resulted in 76% accuracy up to 60 m by using a multilayer perceptron method. The results indicate that there is a potential for production applications and that there is a great need for automatic real-time sensoring in order to produce applicable predictions. 相似文献
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Iwan Wsterlund 《Journal of Terramechanics》1989,26(2)
In forestry operations, machines used should have a high practicability, yet damage the stand as little as possible. Machine forces are undoubtedly too high in many cases, causing deep ruts, soil compaction and cutting off the tree roots. The knowledge of what forces a forest stand can withstand is still quite limited. One of the aims of our project is to supply information about the strength of the forest floor. Since the forest floor of podzol-type is a complex layered structure, we have started by studying the components in the system. A sand sediment can bear high pressures, whereas a moist fine sandy till soil should not be loaded to more than 30 kPa if severe soil compaction is to be avoided. However, the effect of shear forces and slippage is poorly studied. The humus layer above the mineral soil is armoured by tree roots, shrub roots, grass roots, etc. Intact bark is the best guarantee for healthy trees. During the sap period the shear strength of tree root bark is at least 40 N cm−2. The armouring effect of roots and rhizomes on the humus layer is considerable, as the total length of roots may be 200–500 m m−2. The strength of the humus layer is being measured. 相似文献
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In this paper, we develop a method to estimate the bridge deflection using fiber optic Bragg-grating (FBG) strain sensors.
For most structural evaluation of bridge integrity, it is very important to measure the geometric profile, which is a major
factor representing the global behavior of civil structures, especially bridges. In the past, because of the lack of appropriate
methods to measure the deflection curve of bridges on site, the measurement of deflection has been restricted to just a few
discrete points along the bridge, and the measuring points have been limited to the locations installed with displacement
transducers. However, by applying classical beam theory, a formula is rearranged to estimate the continuously deflected profile
by using strains measured directly from several points. In addition, FBG strain sensors, which are electromagnetic, noise-free
and multipoint measurable, are employed to obtain flexural strains more accurately and stably. The regression analysis is
performed to obtain a strain function from the measured strain data. Finally, the deflection curve can be estimated by applying
the strain function to the formula. An experimental test has also been carried out to verify the developed method. 相似文献
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A method of optimal wheel torque determination for electric motor vehicles is presented. Electric motor vehicles are increasing with the rise of public interest in environmental protection. In the case of vehicles driven by controllable motors on each individual wheel, the determination of the wheel torque is an essential factor for efficient driving. In this research, a method of optimal torque determination has been formulated by using the variational principle to minimize frictional work done by the tires with the ground contact. Optimal torque on each wheel for a four-wheel vehicle was numerically obtained by solving the equations under several driving conditions. The result of the numerical simulation is useful as a guide to control the motor torque of electric vehicles for efficient driving. 相似文献
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A model of a snow layer represented by a continuous set of columns whose deformations are described by the nonlinear model of an ideal elastoplastic continuous medium with viscous properties is proposed. Under the action of a rigid wheel on snow, the field of shear stresses is specified by the law of dry friction. Prom the equations of motion describing the plane-parallel motion of the wheel, there are determined a zone of contact of the wheel with snow, the steady motions of the wheel, and a mode of slipping the wheel. The numerical results are given in tables and figures. These results are obtained by solving the nonlinear equations of motion containing definite integrals with variable integration limits. 相似文献
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In order to improve the efficiency of the support vector machine (SVM) for classification to deal with a large amount of samples, the least squares support vector machine (LSSVM) for classification methods is introduced into the reliability analysis. To reduce the coraputational cost, the solution of the SVM is transformed from a quadratic programming to a group of linear equations. The numerical results indicate that the reliability method based on the LSSVM for classification has higher accuracy and requires less computational cost than the SVM method. 相似文献
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提出了一种利用偏置动量轮及推进器实现大角度姿态机动控制的方法。首先建立轨道系下的卫星模型及动量轮推进器的模型,并基于该模型采用动量轮及推进器结合的反馈线性化控制方法,最后设计了大角度机动的参考轨迹。仿真和分析结果表明,文中的控制方法可以在45 s内使卫星机动40°,并在100 s内达到180°大角度,控制精度达到0.4°。可以无需对动量轮进行加减速操作而进行实时的姿态机动。不仅能满足实时性需要,同时可以避免动量轮饱和,降低能源消耗,为微小卫星姿态控制系统的工程实现提供了非常有价值的参考。 相似文献
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《中国惯性技术学报》2020,(2)
行人航位推算是智能手机室内定位与导航系统中最常用的方法,步长估计是重要组成部分。针对现有步长估计模型精度不够高、多数模型无法用于智能手机的问题,提出了一种面向智能手机基于随机森林回归的高精度步长估计模型。利用线性回归和相关分析方法对测试数据进行特征分析,以身高、步频及其算术平方根为训练特征构建随机森林回归模型,采用十折交叉验证法的误差评定结果(相关系数和均方根误差)对随机森林回归模型进行改进。利用提出步长估计模型在4段走廊内开展实验,步行211 m的距离误差为2.582 m,相对误差约为1.22%;与常用三种模型相比,相对误差减小了2.18%~5.82%,且具有更高轨迹重合度。实验结果表明,提出模型比常用三种模型具有更高估计精度。 相似文献
20.
A method is presented for the determination of the coefficient of friction at low sliding speeds down to 3 nm/s. It is also
possible to vary the contact pressure. The maximum average contact pressure is 40 MPa in the present test configuration, where
a servohydraulic tension-torsion machine is used. The method, involving test equipment, measurement and the principles of
evaluation, is exemplified by a study where the variation of the coefficient of friction with sliding velocity contact pressure
and surface roughness is investigated for the material combination steel and concrete. The measurements have been performed
as a 23 factorial design. An error analysis was performed and the relative measurement uncertainty when determining the coefficient
of friction was estinated to be 1.2 percent. 相似文献