Average Traction Force Research Articles

Parameters collaborative optimization design and innovation verification approach for fuel cell distributed drive electric tractor

Fuel cell distributed drive electric tractors (FCDET) are one of the necessary means to achieve truly green agriculture. However, low traction efficiency, poor control coordination, and excessive energy consumption are the main reasons hindering the industrialization of FCDET. This paper proposed a parametric collaborative optimization design method and innovative verification system that considers the drive system and energy system. Based on the tractor plowing operating conditions, a 7-DOF coupled dynamics model of the distributed drive system and a tire-soil interaction model were established, and the key component selection and parameter matching were completed. On the drive system optimization level, the front and rear wheelside transmission ratios are optimized based on a multi-island genetic algorithm (MIGA). On the energy system optimization level, the globally optimal power distribution ratio is found based on the dynamic programming algorithm (DP). A complete experimental prototype verification system is constructed based on the MATLAB/Simulink-NI PXI joint simulation platform, physical prototype test bench, and real vehicle multi-index test platform. The results show that the average efficiencies of the optimized drive and energy system are increased by 0.38 % and 3.82 %, the total energy consumption (total hydrogen consumption) is reduced by 25.40 % and 15.39 %, respectively. The maximum fault-free operating time is 5.5h, the average traction power is 21.07 kW, and the average traction force is 10610 N in the all-wheel drive mode. The experimental results fully demonstrate that the electric tractor with the fuel cell distributed drive system as the core can meet the verification of multiple indicators. This study can provide a new theoretical basis and technical verification method for the optimal design and system control of fuel cell distributed drive electric tractors.

Fatigue integrity assessment for tractor-mounted garlic-onion harvester

Tractor-mounted harvesters are operated under harsh conditions to dig deep-rooted crops on irregular soil conditions. Therefore, it is important to evaluate their fatigue strength by measuring random load characteristics that occur during operation. Based on this, highly reliable fatigue design that can be used safely without damage during the service life is required. In this study, the traction force of a tractor-mounted garlic-onion harvester was measured through a field test, and its fatigue damage was calculated based on the Rain-flow counting method and Goodman’s equation. In addition, a method of verifying the fatigue safety of the harvester by calculating the equivalent load and required test cycle for the accelerated life test in the laboratory was presented. The average traction force calculated from the torque history measured in field tests by attaching a torque meter to four tractor wheels at the actual harvesting site was found to be 8.51 kN. When the accelerated life test condition corresponding to the target life of 800 h was calculated using the presented method, the number of load cycles required under a maximum load of 12.37 kN and a minimum load of 7.56 kN was found to be 2.67 × 106 cycles.

A comparative study of the application-based properties of hot melt adhesives (HMAs) formulated with different waxes

In this study, three chemically similar but morphologically different high melting hydrocarbon waxes having similar DSC peak melting temperatures were analysed, and the influence of their molecular architectures on hot melt adhesive (HMA) performance, was evaluated. Selected waxes included each of the following types: Fischer Tropsch wax (FT), by-product polyethylene wax (BPPE) and first intention polyethylene wax (FIPE). Both, ethylene-co-vinyl acetate (EVA) and metallocene catalysed polyethylene (mPE) based HMAs were formulated. The high chain linearity of FT wax resulted in faster crystallization and faster adhesive set times as well as higher peel adhesion, shear adhesion and IOPP heat resistance temperatures. Wax viscosities were in direct correlation with resultant HMA viscosities. EVA HMAs had longer set times and were more prone to thermal degradation upon prolonged exposure to elevated temperatures and was most pronounced for FIPE wax. Average traction force was dependent on the open time and wax/polymer combination with FT showing a smaller open time window for both EVA and mPE based HMAs.

Direct Force Measurement of the PANC-1's Traction Force

Cell migration is responsible for positive responses in one's body in aid of healing of wounds, or infamously, invasion of cancer cells through the connective tissues. To better understand these major physiological phenomena, quantification of traction forces is necessary. The most common method to use is Traction Force Microscopy (TFM). Polystyrene fluorescent beads were embedded in the substrate as markers, traction force is then recovered from particle displacements. However, such setup has no control over marker positions and often introduce background noise, e.g. loss of spatial resolution. In addition, beads usually aren’t in direct contact with the cells, hence the measurement has a higher degree of estimation due to extrapolations and modeling. Thus, we have employed fluorescent superparamagnetic beads as detection markers. During the polymerization process of the polyacrylamide gel, an external magnetic field is applied and a single layer of superparamagnetic beads formed along the surface of the substrate. Such configuration reduces background noise, improving the spatial resolution to 5-nm for XY plane. Since the magnetic beads are located at the surface, marker (magnetic beads) positions are directly influenced by traction forces, improving the accuracy of measurements too. Polyacrylamide gels of 1, 2, 4, through 25 kPa stiffness were used for the traction force measurement. The maximum traction force through the 12-hour cellular phase is measured to be 3.7 nN in 2kPa, while the average traction force is registered to be 1.2 nN in 2 kPa. Increasing stiffness doesn’t change the maximum traction force, but increases the average force. The directions of the traction force exerted on the cell were analyzed for comparison.

Real-time measurement of cell contractile force during activation of human hepatic stellate cell line LX-2

The contractile force of hepatic stellate cells plays a very important role in liver damage, hepatitis and fibrosis. In this paper, a method based on polydimethylsiloxane (PDMS) thin micropillar arrays is proposed to measure the contractile force of human hepatic stellate cell line LX-2, which enables dynamic measurement of the subcellular distribution of force magnitude and direction. First, thin micropillar arrays on glass bottom dish were fabricated using two-step casting process in order to meet the working distance requirement of 100× objective lens. After hydrophilic treatment and protein imprint, cells were seeded on the micropillar arrays. LX-2 cells, which were quiesced by growth in serum-free medium, were activated by adding fetal bovine serum (FBS). The deflections of the micropillars were achieved by image processing technique, and then the contractile force of cells exerted on the micropillars was calculated according to mechanical simulation results, and was analyzed under both quiescent and activated conditions. The experimental results show that the average traction force of quiescent cells is about 20 nN, while the contractile force of activated cells increased to 110 nN upon adding FBS. This method can quantify the contractile force of LX-2 cell on subcellular scale in both quiescent and activated states, which may benefit pathology study and drug screen for chronic liver diseases resulted from liver fibrosis.

Optimal design of the gear ratio of a power reflux hydraulic transmission system based on data mining

The power reflux hydraulic transmission system (PRHTS) with a capacity adjustment device presents a high transmission efficiency, a wider range of high-efficiency area (η ≥ 75%), low speed, high torque, and adjustable capacity factor to correspond to the various working modes of a wheel loader. Herein, based on the working principle of a capacity adjustment device and cluster analysis of V-pattern working condition data, the shift strategy of a capacity adjustment device was designed. By combining the output characteristics of the PRHTS and V-pattern working condition data analysis, the optimal gear ratio was developed. The simulation results demonstrated that, in a V-pattern working condition, the average transmission efficiency of the PRHTS and traction were improved by 6.94% and 8.74%, respectively, based on the shovel efficiency and fuel consumption which are consistent with the traditional hydraulic transmission system. In traction conditions, the average traction force increased by 20.92%, the dynamic factor increased by 19.75%, and the average constant-speed fuel consumption per 100 km decreased by 11.66%, which considerably improved the power and fuel economy of the wheel loader during traction conditions.

Qualitative analysis of the undesirable effect of loss of traction force of a vehicle during an intense start

The effect of a significant and sharp loss of the average traction force during vehicle acceleration with asymmetric or asynchronous vibrations of the driving wheels is found. The effect manifests itself in vehicles with an inter- wheel differential under an intensive start with slipping. The vibrational modes leading to both partial and almost complete loss of the average traction force are specified. It can be dangerous when entering highways or crossing unregulated intersections.

Qualitative Analysis of the Undesirable Effect of Loss of Traction Force of a Vehicle during an Intense Start

The effect of a significant and sharp loss of the average traction force upon vehicle acceleration during asymmetric or asynchronous vibrations of the driving wheels is found. The effect manifests itself in vehicles with an interwheel differential under an intensive start with slip. The vibrational modes leading to both partial and almost complete loss of the average traction force are specified. It can be dangerous when driving on highways or crossing unregulated intersections.

The Loading Control Strategy of the Mobile Dynamometer Vehicle Based on Neural Network PID

To solve the problems of low loading precision, slow response speed, and poor adaptive ability of a mobile dynamometer in a tractor traction test, a PID control strategy based on a radial basis function neural network with self-learning and adaptive ability is proposed. The mathematical model of the loading system is established, the algorithm of adaptive control is described, and the loading control method is simulated with MATLAB software. The system, which uses the NN-PID (neural network PID) control strategy, is used to test a YTO-MF554 tractor. Then, the proposed control strategy is validated. Results show that when the traction increases from 0 to 10 kN, the response time of the test system is 1.5 s, the average traction force in the stability range is 10.13 kN, and the maximum relative error of traction force is 2.2%. This control strategy can improve the response speed and steady-state accuracy and enhance the adaptive ability of the mobile dynamometer vehicle loading system. This study provides a reference for designing the adaptive controller of the mobile dynamometer vehicle loading system.

A novel assessment of the traction forces upon settlement of two typical marine fouling invertebrates using PDMS micropost arrays.

ABSTRACTMarine biofouling poses a severe threat to maritime and aquaculture industries. To prevent the attachment of marine biofouling organisms on man-made structures, countless cost and effort was spent annually. In particular, most attention has been paid on the development of efficient and environmentally friendly fouling-resistant coatings, as well as larval settlement mechanism of several major biofouling invertebrates. In this study, polydimethylsiloxane (PDMS) micropost arrays were utilized as the settlement substrata and opposite tractions were identified during early settlement of the barnacle Amphibalanus amphitrite and the bryozoan Bugula neritina. The settling A. amphitrite pushed the periphery microposts with an average traction force of 376.2 nN, while settling B. neritina pulled the periphery microposts with an average traction force of 205.9 nN. These micropost displacements are consistent with the body expansion of A. amphitrite during early post-settlement metamorphosis stage and elevation of wall epithelium of B. neritina during early pre-ancestrula stage, respectively. As such, the usage of micropost array may supplement the traditional histological approach to indicate the early settlement stages or even the initiation of larval settlement of marine fouling organisms, and could finally aid in the development of automatic monitoring platform for the real-time analysis on this complex biological process.

Role of Mechanical Cues in Cell Differentiation and Proliferation: A 3D Numerical Model.

Cell differentiation, proliferation and migration are essential processes in tissue regeneration. Experimental evidence confirms that cell differentiation or proliferation can be regulated according to the extracellular matrix stiffness. For instance, mesenchymal stem cells (MSCs) can differentiate to neuroblast, chondrocyte or osteoblast within matrices mimicking the stiffness of their native substrate. However, the precise mechanisms by which the substrate stiffness governs cell differentiation or proliferation are not well known. Therefore, a mechano-sensing computational model is here developed to elucidate how substrate stiffness regulates cell differentiation and/or proliferation during cell migration. In agreement with experimental observations, it is assumed that internal deformation of the cell (a mechanical signal) together with the cell maturation state directly coordinates cell differentiation and/or proliferation. Our findings indicate that MSC differentiation to neurogenic, chondrogenic or osteogenic lineage specifications occurs within soft (0.1-1 kPa), intermediate (20-25 kPa) or hard (30-45 kPa) substrates, respectively. These results are consistent with well-known experimental observations. Remarkably, when a MSC differentiate to a compatible phenotype, the average net traction force depends on the substrate stiffness in such a way that it might increase in intermediate and hard substrates but it would reduce in a soft matrix. However, in all cases the average net traction force considerably increases at the instant of cell proliferation because of cell-cell interaction. Moreover cell differentiation and proliferation accelerate with increasing substrate stiffness due to the decrease in the cell maturation time. Thus, the model provides insights to explain the hypothesis that substrate stiffness plays a key role in regulating cell fate during mechanotaxis.

Migration, Force Generation and Mechanosensing of Cells in Collagen Gels

Collagen gels are frequently used to study cell migration in a three-dimensional environment. Mechanical properties of collagen gels are governed by non-affine deformation of the collagen fibrils, such as buckling and tautening, resulting at the macroscopic scale in strain stiffening under shear and a strong lateral contraction under stretch. It is currently unknown how these macroscopic properties play out at the scale of a migrating cell, and how this depends on the cell geometry. To explore this question, we develop a non-linear elastic material model for collagen gels based on observations from confocal microscopy that fibrils can evade mechanical stress using their internal degrees of freedom. This non-affine behavior results in a non-linear force length relationship of fibril segments and leads to a macroscopic strain stiffening and lateral contraction. In particular, we show that tautening of fibrils results in a strong material stiffening against expanding forces, e.g. from a migrating cell with a diameter larger than the network pore diameter. By this mechanism, even a soft collagen gel can sterically constrain a migrating cell. Using our material model, we compute cell traction forces, induced stresses as well as material stiffening, from collagen fiber displacements during the migration of MDA-MB 231 breast carcinoma cells through dilute (0.6 mg/ml, Young's modulus 85 Pa) and dense (2.4 mg/ml, Young's modulus 1100 Pa) collagen gels. We find that cells exert highly localized forces onto the matrix, leading to a localized ∼2-fold material stiffening. However, the average traction force magnitude increases with collagen concentration by ∼3-fold, from 40nN in dilute gels to 120nN in dense gels. This observation may help explain why cells can migrate more efficiently in stiffer gels, despite their narrower pore diameter.

The development of an apparatus to understand the traction developed at the shoe–surface interface in tennis

The traction developed at the shoe–surface interface can have a significant influence on a player’s injury risk and performance in tennis. The purpose of this study was to investigate shoe–surface traction on a dry acrylic hard court and two artificial clay court tennis surfaces in dry and wet conditions. A laboratory-based mechanical test rig was developed to measure the traction force developed at the shoe–surface interface. Linear regression analysis was used to examine the relationship between normal force and three measures of traction: initial stiffness, peak traction force and average dynamic traction force. The normal force did not significantly influence the initial stiffness for the shoe–surface system on the acrylic hard court but did on the artificial clay surfaces. The infill particle size and the addition of moisture influenced the traction developed on the artificial clay surfaces. Small, dry particles developed greater traction and with a sufficiently high applied normal force will provide traction comparable to that on an acrylic hard court. However, increased particle size and/or the presence of moisture generally reduced traction. Strong and significant positive linear relationships were found between peak traction force and average dynamic traction force for all surface types and conditions. This study improves the understanding of the influence surface characteristics have on shoe–surface traction mechanisms. Once traction mechanisms are understood, surface properties and/or footwear can be effectively changed to maximise performance and/or minimise injury risk.

Vacuum-assisted vaginal delivery simulation – quantitation of subjective measures of traction and detachment forces

Objective: Excessive traction has been alleged as the cause of newborn complications associated with vacuum delivery. We sought to quantify subjective levels of physician vacuum traction in a simulated obstetric delivery model, dependent upon level of training. Methods: Three groups of physicians, based on training level applied traction (minimal, average, maximal) on a pre-applied vacuum model and forces were continually recorded. Detachment force was recorded with traction in both the pelvic axis and at an oblique angle. Results: Quantified traction force increased from subjective minimal to average to maximal pulls. Within each level, there were no differences between the groups in the average traction force. Detachment force was significantly less when traction was applied at an oblique angle as opposed to the pelvic axis (11.1 ± 0.3 vs 12.2 ± 0.3 kg). Conclusion: Providers appear to be good judges of the force being applied, as a clear escalation in force is noted with minimal, average and maximal force pulls. There appears to be a relatively short learning curve for use of the vacuum, as junior residents’ applied force was not different from those of more experienced practitioners. Using the KIWI device, detachment force is lower when traction is applied at an oblique angle.

중형 트랙터용 원형베일러 성능평가

Bale is an operation of collecting livestock feed materials from field crop residue, and mechanization demand on the operation has been increased. Bailers imported from foreign countries such as Japan and European countries have been used, but those models showed improper performance in Korean situations. In recent years, a steel-roller type round baler attachable to medium size tractors(40 to 60 HP) for effective bale operation in Korea was developed. This study was conducted to evaluate field performance of the baler. For proper baling operation, engine speed was greater than 1,800rpm, average traction force and PTO torque were about 4kN and in a range of 380-671Nm, and maximum values were about 7kN and 3,000Nm, respectively. Performance evaluation tests for sudan grass, rice straw, and blue barley showed that field capacity was 0.59ha/h for blue barley and 0.99ha/h for sudan grass and rice straw. Bale weight, diameter, width, and bulk density were in ranges of 176.1~418.4㎏, 1.07~1.12m, 1.02~1.04m, and 175.3~454.1㎏/㎥. Noise sound level during the baling operation was 4㏈ greater than idle operation condition, which was considered to be ignorant.

Mechanical Forces in Endothelial Cells during Firm Adhesion and Early Transmigration of Human Monocytes

Transmigration of leukocytes across the endothelial barrier is a tightly controlled process involving multiple steps, including rolling adhesion, firm adhesion, and then penetration of leukocytes through the endothelial monolayer. While the key molecular signals have been described in great detail, we are only just beginning to unveil the mechanical forces involved in this process. Here, using a microfabricated system that reports traction forces generated by cells, we describe forces generated by endothelial cells during monocyte firm adhesion and transmigration. Average traction force across the endothelial monolayer increased dramatically when monocytes firmly adhered and transmigrated. Interestingly, the endothelial cell that was in direct contact with the monocyte exhibited much larger traction forces relative to its neighbors, and the direction of these traction forces aligned centripetally with respect to the monocyte. The increase in traction force occurred in the local subcellular zone of monocyte adhesion, and dissipated rapidly with distance. To begin to characterize the basis for this mechanical effect, we show that beads coated with anti-ICAM-1 or VCAM-1 antibodies bound to monolayers could reproduce this effect. Taken together, this study provides a new approach to examining the role of cellular mechanics in regulating leukocyte transmigration through the endothelium.

Assessment of Spinal Flexibility in Adolescent Idiopathic Scoliosis

Prospective evaluation of a new suspension test to determine curve flexibility in adolescent idiopathic scoliosis (AIS) in comparison with erect side-bending. To verify whether the suspension is a better method than side-bending to estimate curve reducibility and to assess spine flexibility. Spinal flexibility is a decisive biomechanical parameter for the planning of AIS surgery. Side-bending is often referred as the gold standard, but it has a low reproducibility and there is no agreement amongst surgeons about the most advantageous method to use. Even more, every technique evaluates reducibility instead of flexibility since the forces involved in the change in shape of the spine are not considered. Eighteen patients scheduled for AIS surgery were studied. Preoperative radiological evaluation consisted of 4 radiographs: standing posteroanterior, left and right erect side-bending, and suspension. The side-bending and the suspension tests were compared on the basis of the apical vertebrae derotation and the scoliosis curve reduction. Frontal and axial flexibility indices, expressed as the ratio between the moment induced by the body weight and the reduction, were calculated from the suspension data. The average scoliosis curve reduction and apical vertebra derotation were 21 degrees (37%) and 3 degrees (12%), respectively for erect side-bending and 26 degrees (39%) and 7 degrees (28%), respectively for suspension. The erect side-bending test generated a larger curve reduction (P = 0.05) when considering the moderate curves only and the suspension test (P = 0.02) when considering the severe curves. The suspension test produced a larger axial derotation (P = 0.007) when considering all the curves. The average traction force during suspension was 306 N (187 N-377 N). The average estimation for the frontal flexibility index was 1.64 degrees/Nm (0.84-2.82) and 0.51 degrees/Nm (0.01-1.39) for the axial flexibility index. Results of this study demonstrate the feasibility to really evaluate the spine flexibility with the suspension test. The estimated flexibility values are realistic and similar to those reported in vitro. Suspension should be used in the future for spine flexibility assessment.

Analysis of traumatic brain injury due to primary head contact during vehicle-to-pedestrian impact

We developed a 50th-percentile American male pedestrian model including a detailed brain, and the mechanical responses and kinematic biofidelity predicted by this model were validated against the available cadaveric test data. Vehicle-to-pedestrian impact simulations were then performed to investigate a potential mechanism for traumatic brain injury resulting from a lateral blunt impact to the head. Due to inertia of the brain mass, it was found that the average traction force produced in the cervical spinal cord exceeded 50 N in the impact involving a sport utility vehicle and 25 N in the impact involving a sedan, when the striking vehicle was travelling at 40 km/h. This inertial loading may play a key role in a brainstem, or upper-cervical-cord, lesion occurring before head strike. Results of this study suggest that close attention should be paid to pedestrian kinematics during free flight even before the head makes primary contact with the striking vehicle.

Robot-assisted femoral fracture reduction: Preliminary study in patients and healthy volunteers

We developed a robot-assisted fracture reduction system (FRAC-Robo) to assist anatomical reduction and to maintain reduction during internal fixation while recording the procedure in a log. We conducted two experiments before using FRAC-Robo clinically. In the first experiment using the FRAC-Robo system, we measured the maximum force and torque required to pull and rotate the limbs of healthy conscious volunteers until they felt pain or abnormality. The average maximum traction force applied to the lower limb was 250.7 N, and the average maximum torque was 5.6 Nm in internal rotation and 7.6 Nm in external rotation for 30° of abduction of hip. In the second experiment, we measured the traction force and rotation torque during the reduction of proximal femoral fractures. The average traction force and rotation torque needed for reduction were 215.9 N and 3.2 Nm, respectively. On the basis of these results, we consider that FRAC-Robo can generate sufficient force and torque to reduce femoral fractures safely.

Robot-assisted femoral fracture reduction: Preliminary study in patients and healthy volunteers

We developed a robot-assisted fracture reduction system (FRAC-Robo) to assist anatomical reduction and to maintain reduction during internal fixation while recording the procedure in a log. We conducted two experiments before using FRAC-Robo clinically. In the first experiment using the FRAC-Robo system, we measured the maximum force and torque required to pull and rotate the limbs of healthy conscious volunteers until they felt pain or abnormality. The average maximum traction force applied to the lower limb was 250.7 N, and the average maximum torque was 5.6 Nm in internal rotation and 7.6 Nm in external rotation for 30° of abduction of hip. In the second experiment, we measured the traction force and rotation torque during the reduction of proximal femoral fractures. The average traction force and rotation torque needed for reduction were 215.9 N and 3.2 Nm, respectively. On the basis of these results, we consider that FRAC-Robo can generate sufficient force and torque to reduce femoral fractures safely.