An instrumentation system to measure the loads acting on the tractor PTO bearing during rotary tillage

Application of rotary tillage has been increased due to less tillage passes required, reduced draft, and greater efficiency through reduction in wheel slippage. Early failure of the bearing of tractor power take-off (PTO) shaft was observed in tractors of power range 30–35 horsepower during rotary tillage. An instrumentation setup involving an extended octagonal ring transducer (EORT) was developed and installed at the bottom of the bearing to measure the axial load and the vertical component of the radial load. The horizontal component of radial load was measured by strain gauges. Based on measured loads, the bearing life was assessed. Independent variables were: operating depth, number of blades, gear setting, engine speed, and tyre size. The average axial and radial loads varied from 786–3869 N, and 134–430 N, respectively. However, bearing experienced very high peak loads during each trial. The peak axial and radial loads was recorded between 1081–7534 N and 566–1794 N, respectively. The estimated bearing life based on peak loads was 171.98–28341.39 h. Based on the findings, it may be concluded that the average loads were not sufficient to cause quick failure of PTO bearing, rather sudden peak loads might be the root cause of early failure.     

Fuzzy logic based automatic slip control system for agricultural tractors

In this study, a fuzzy-based automatic slip control system was developed for agricultural tractors. The developed system continuously measures the amount of slip that occurs during the tillage activities and automatically changes the operation depth of tillage equipment according to the amount of increase in the slip value. The amount of slip occurring on the driving wheels was applied as a separate input to the designed fuzzy control system (FCS) and at the fuzzy rule base, it was decided how much the depth of tillage would be reduced. The system was mounted on an agricultural tractor and trials were carried out in actual field conditions. The results of the tillage trials performed with the developed FCS were compared separately with the results of the tillage trials performed with an operator control (OC) without using any automatic control system. As a result of the trials, compared to the operator control, it was determined that in the tillage activities carried out with FCS, there were 42% decreases in slip values, 30% decreases in draft force values, 44% decreases in fuel consumption values and 5% increases in field work performance values. It was also observed that there were 10% changes in tillage depth.     

Analysis of the PTO load of a 75 kW agricultural tractor during rotary tillage and baler operation in Korean upland fields

In this paper, the PTO severeness of an agricultural tractor during rotary tillage and baler operation was analyzed. The S–N curves of the PTO driving gears were obtained through fatigue life test. To obtain the S–N curves of the PTO driving gears, the breakage time and rotational speed of the gears were measured through observation of the bending stress with changing torque. The torque acting on the PTO was measured and analyzed during rotary tillage and baler operation. Rotary tillage and baler operation were conducted at two ground speeds and two PTO rotational speeds at upland field sites with similar soil conditions, respectively. The load data were inverted to a load spectrum using rain-flow counting and SWT equations. Modified Miner’s rule was used to calculate the partial damage sum. The severeness was defined as the relative ratio of the damage sum. The results showed that the damage of the PTO increased when the ground speed or the PTO rotational speed increased. The effect of the PTO rotational speed on the severeness of the PTO was more significant than that of the ground speed. The severeness of the PTO of rotary tillage was greater than that of baler operation.     

Power spectral density analysis of draft and torque fluctuations of a PTO powered disk tiller

Experiments were conducted in a typical Bangkok clay soil with a PTO driven disk tiller to collect the draft force and torque variation data. Tests were conducted at different forward speeds of 0.29, 0.59, 0.86, 1.08 and 1.37 m/s and at 28° and 33° disk gang angle settings. Average soil moisture content was 26% and average cone index of the test soil was 1870 kPa during all the tests. The draft force was measured by a three point linkage dynamometer. The PTO torque was measured by a slip ring type torque transducer. Tests were also conducted in the unpowered mode. Fast Fourier transform (FFT) and power spectral density (PSD) analysis techniques were used to analyse the draft force and torque variations in a time domain. The results indicated that the dominant frequencies of the draft force variations were within the range of 2.5–5.5 cycles/m of forward travel. The wave length was longer at a higher disk gang angle setting. The dominant frequency component of the torque variations varied from 3.3 to 4.3 cycles/revolution of the disk. In the unpowered mode the dominant frequencies of the draft signals had less magnitude than those of the powered mode for the same operating conditions at both disk gang angle settings of the powered disk.     

Computerized instrumentation system for monitoring the tractor performance in the field

A high precision computerized instrumentation package was developed and mounted on a 50 kW tractor to monitor and measure various performance parameters of a tractor and implement system. The system was intended to be used for the compilation of a database of draft requirements of tillage implements. The system designed to measure: three-point linkage forces, ground speed, tillage depth, fuel consumption, forward speed, slip, engine speed, hydraulic pressure and fluid temperatures. The data acquisition unit was based on a high speed multi processors Campbell Scientific CR3000 data logger linked to a microcomputer using suitable transducer. The average calibration constants for the rear wheel speed, fuel consumption and three point linkage transducers were 0.0364 m/pulse, 0.000142857 l/pulse and 0.66 mV/kN respectively. The data acquisition system was capable of scanning rate up to 100 K sample/s. Data acquisition system was developed to measure draft of primary tillage implements in vertisol.     

Determination of rating cone index using wheel sinkage and slip

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.     

Development and implementation of an IOT based instrumentation system for computing performance of a tractor-implement system

A high precision and compact IOT based digital instrumentation setup to measure, display and record various tractor and implement system performance parameters was developed and installed on a 28.3 kW Tractor. The setup was capable of continuous monitoring and wirelessly transmitting tractor-implement performance parameters on a cloud platform such as engine speed, radiator fan speed, fuel consumption, draft, forward speed, lift arm angle, wheel slip, wheel slip, PTO speed, geo-location/position of the tractor, choking of seeds in the implement and vibrations experienced by the implement. For precision measurements, commercial transducers used in the system were calibrated and assessed under both static and dynamic conditions. The average calibration constant for fuel consumption, forward speed, lift arm angle and load cell were 0.00009804 L/pulse, 0.01610306 km/h/pulse, 0.056 mA/degree and 0.2575 mV/kN respectively. The system based on DataTaker DT 85 Data logger connected to a micro-computer through transducers capable of transferring data wirelessly was installed on John Deere 5038 tractor and was tested with a Spatially Modified No-Till Drill in agricultural field with varied implement depth.     

Evaluation of a 6.71 kW power tiller for draft and drawbar power on tar roads

A 6.71 kW power tiller was evaluated for draft and drawbar power on tar roads. The effect of mounting 40 kg of wheel ballast was also studied. Polynomial regression analysis was used to establish the relationship between draft and wheel slip, drawbar power and wheel slip, drawbar power and fuel consumption, and drawbar power and specific fuel consumption. The results of the study showed draft values of 2107, 2110 and 2110 N in second low, third low and first high gears at an engine speed of 150o rpm with a 15% wheel slip. The respective draft values at engine speed of 2000 rpm with a 15% wheel slip were 2172, 2189 and 2212 N. With the mounting of 40kg wheel ballast there was an increase in draft of 217, 207 and 291 N at 1500 rpm, and 328, 306 and 344 N at 2000 rpm of the engine with a 15% wheel slip in second low, third low and first high gears, respectively. The increase in drawbar power with 40 kg ballast was 10.88%, 7.83% and 20.13% at 1500 rpm and 18.89%, 16.56% and 14.88% at 2000 rpm of engine over the drawbar power available with zero ballast. The fuel consumption with the use of wheel ballast was slightly more than the fuel consumption without any ballast.     

Estimating wheel slip for a forest machine using RTK-DGPS

Wheel slip may increase the risk for wheel rutting and tear up ground vegetation and superficial roots and thereby decreasing the bearing capacity of the ground, but also reducing the growth of nearby standing forest trees. With increased slip, more energy is consumed for making wheel ruts in the ground, with increased fuel consumption as a result. This paper proposes a novel method for measuring slip in an uneven forest terrain with an 8WD forestry machine. This is done by comparing the wheel velocity reported by the machine and velocity measured with an accurate DGPS system. Field tests with a forestry machine showed that slip could be calculated accurately with the suggested method. The tests showed that there was almost no slip on asphalt or gravel surfaces. In a forest environment, 10–15% slip was common. A future extension of the method enabling estimation of the slip of each wheel pair in the bogies is also suggested.     

An indoor traction measurement system for agricultural tires

To reliably study soil–wheel interactions, an indoor traction measurement system that allows creation of controlled soil conditions was developed. This system consisted of: (i) single wheel tester (SWT); (ii) mixing-and-compaction device (MCD) for soil preparation; (iii) soil bin; (iv) traction load device (TLD). The tire driving torque, drawbar pull, tire sinkage, position of tire lug, travel distance of the SWT and tire revolution angle were measured. It was observed that these measurements were highly reproducible under all experimental conditions. Also relationships of slip vs. sinkage and drawbar pull vs. slip showed high correlation. The tire driving torque was found to be directly influenced by the tire lug spacing. The effect of tire lug was also discussed in terms of tire slip.     

Draftability of a 8.95 kW walking tractor on tilled land

A 8.95-kW walking tractor was evaluated for draft and drawbar power on tilled land. Empirical equations were developed to correlate the relationship between draft and wheel slip, drawbar power and wheel slip and drawbar power and fuel consumption. The values of draft, drawbar power and specific fuel consumption were calculated at 25% wheel slip. The results indicated that the values of draft on tilled land with pneumatic wheels at engine speed of 2000 rpm were 803 and 773 N in second low and third low gears, respectively. The respective draft values at engine speed of 1500 rpm were 748 and 735 N in second low and third low gears under slightly loose soil conditions. Mounting of a 40-kg wheel ballast increased the value of draft to 901 and 921 N at an engine speed of 2000 rpm and 872 and 888 N at an engine speed of 1500 rpm in second low and third low gears. Replacement of pneumatic wheels by steel wheels further increased the draft readings to 1034 and 999 N at an engine speed of 2000 rpm and 913 and 935 N at engine speed of 1500 rpm in second low and third low gears, respectively, indicating significant increase in drawbar power both at 2000 and 1500 rpm in second low and third low gears with the use of steel wheels. The specific fuel consumption decreased by about 28% and 27% at engine speed of 2000 rpm and about 17% and 21% at engine speed of 1500 rpm in second low and third low gear with the use of steel wheels over pneumatic wheels without wheel ballast. The specific fuel consumption decreased by about 4% and 14% at engine speed of 2000 rpm and 7% and 23% at engine speed of 1500 rpm in second low and third low gears, respectively, with the use of steel wheels over pneumatic wheels with 40 kg wheel ballast.     

Effect of rotation direction of a rotary tiller on draft and power requirements in a Bangkok clay soil

Experiments were conducted in a Bangkok clay soil to evaluate the performance of a rotary tiller equipped with reverse or conventional blades. The conventional rotary tiller was equipped with C-type blades whereas the reverse-rotary tiller had new types of blades. Tests were conducted on wet land as well as in dry land. Tests were conducted at tractor forward speeds of 1.0, 1.5 and 2.0 km/h. A power-take-off (PTO) power consumed was calculated from the PTO torque and speed. The results indicated that the PTO power consumption was less for the reverse-rotary tiller compared to the conventional tiller for all passes and forward speeds. For both rotary tillers, power consumption decreased as the number of passes increased, whereas power consumption increased when the forward speed was increased. At all forward speeds, the power consumption was the highest during the first pass and lowest during the third pass. The maximum difference of PTO power requirement was after the first pass at 1.0 km/h forward speed. The reverse-rotary tiller consumed about 34% less PTO power under this condition.     

Tractive performance of a bulldozer running on weak ground

To determine the tractive performance of a bulldozer running on weak ground in the driven state, the relations between driving force, drawbar pull, sinkage, eccentricity and slip ratio have been analysed together with each energy balance; effective input energy, sinkage deformation energy, slippage energy and drawbar pull energy. It is considered that the thrust is developed not only on the main straight part of the bottom track belt but also on parts of the front idler and rear sprocket, and the compaction resistance is calculated from the amount of slip sinkage. For a given vehicle and soil properties, it is determined that the drawbar pull increases directly with the slip ratio and reaches about 70% of the maximum driving force. The compaction resistance reaches about 13% of the maximum driving force. The sinkage of the rear sprocket, the eccentricity, and the trim angle increase with the increment of slip ratio due to the slip sinkage. These analytical results have been verified experimentally. After determining the optimum slip ratio to obtain a maximum effective tractive power, it is found that a larger optimum drawbar pull at optimum contact pressure could be obtained for a smaller eccentricity of vehicle center of gravity and a larger track length-width ratio under the same contact area.     

The effect of velocity on rigid wheel performance

A simulation model to predict the effect of velocity on rigid-wheel performance for off-road terrain was examined. The soil–wheel simulation model is based on determining the forces acting on a wheel in steady state conditions. The stress distribution at the interface was analyzed from the instantaneous equilibrium between wheel and soil elements. The soil was presented by its reaction to penetration and shear. The simulation model describes the effect of wheel velocity on the soil–wheel interaction performances such as: wheel sinkage, wheel slip, net tractive ratio, gross traction ratio, tractive efficiency and motion resistance ratio. Simulation results from several soil-wheel configurations corroborate that the effect of velocity should be considered. It was found that wheel performance such as net tractive ratio and tractive efficiency, increases with increasing velocity. Both, relative wheel sinkage and relative free rolling wheel force ratio, decrease as velocity increases. The suggested model improves the performance prediction of off-road operating vehicles and can be used for applications such as controlling and improving off-road vehicle performance.     

Wheel slip measurement in 2WD tractor

A microcontroller-based slip sensor was developed for a 2WD tractor to indicate slip values during on-farm use. The ‘zero condition’ considered for the development of slip sensor was – tractor supplied with a driving torque to propel any device across a tarmacadam surface while delivering zero net traction (self-propelled condition). This sensor comprised of four components: power supply; sensing of throttle position, gear position, and wheel rpm; processing of collected data; and display unit. Power was taken from the tractor battery. Rotary potentiometer and proximity switches were installed on the tractor to measure throttle position and wheel revolution, respectively. The performance of developed slip sensor was evaluated both on tarmacadam surface as well as in the field. The variations between indicated and actual slip were found to be within 0–5% for both the surfaces, thus indicating the accuracy of slip measurement by the developed slip sensor.     

Discrete element method analysis of single wheel performance for a small lunar rover on sloped terrain

The purpose of this study is to analyze the performance of a lugged wheel for a lunar micro rover on sloped terrain by a 2D discrete element method (DEM), which was initially developed for horizontal terrain. To confirm the applicability of DEM for sloped terrain locomotion, the relationships of slope angle with slip, wheel sinkage and wheel torque obtained by DEM, were compared with experimental results measured using a slope test bed consisting of a soil bin filled with lunar regolith simulant. Among the lug parameters investigated, a lugged wheel with rim diameter of 250 mm, width of 100 mm, lug height of 10 mm, lug thickness of 5 mm, and total lug number of 18 was found, on average, to perform excellently in terms of metrics, such as slope angle for 20% slip, power number for self-propelled point, power number for 15-degree slope and power number for 20% slip. The estimation of wheel performance over sloped lunar terrain showed an increase in wheel slip, and the possibility exists that the selected lugged wheel will not be able to move up a slope steeper than 20°.     

Measuring the mobility parameters of forwarders using GPS and CAN bus techniques

Use of a datalogger connected to the CAN bus of an 8-wheeled forwarder’s hydrostatic transmission permits measurement of the gross power on the driveline and the rotational velocity of the drive axle. The ground velocity and trajectory of the forwarder is monitored by the GPS technique. These data allow the total resistance force and wheel slip to be determined under different terrain conditions. In this paper the total resistance force is segregated into rolling, slope and winding resistances. The measuring system was tested in practice on an even tarmac surface and a gently sloping hard earth road, the number of input variables in the first tests having been reduced. It was found that the measuring accuracy permitted detection of about a half percent variation in slope inclination in the test lane. Tests on a figure of 8 track showed that the winding resistance can also be detected. It was concluded that the measuring technique is accurate enough for terramechanical research and practicable under real forestry conditions.     

Wall slippage with siloxane gum and silicon rubbers

A slip analysis has been developed to calculate the slip velocities from the capillary rheometry data for a polydimethylsiloxane (PDMS) gum, and two silicon rubber compounds. The analysis generalises the classical Mooney method [J. Rheol. 2 (1931) 210–222] to incorporate the influence of die geometry on the slip behaviour. For the PDMS gum, no slippage was observed below a stress level of about 60 kPa, and there was a jump in the slip velocity at a stress level of about 80 kPa. The complex rheological behaviour of the rubbers meant that the analysis was only applicable at higher stress levels. For each material, a reasonable fit to the slip velocity was obtained using a generalised Navier slip law, which can easily be implemented into computational fluid dynamic simulations. Ultimately, a more realistic slip law is required to model the observed flow behaviour correctly.     

Structure design and traction trafficability analysis of multi-posture wheel-legs bionic walking wheels for sand terrain

Nowadays, the existing walking wheels still have problems with the wheel-legs structure and the traction trafficability on the loose sand. It is commonly believed that African ostrich (Struthio camelus) is a kind of bipedal species with superior running performance on the sandy environment. Being enlightened by this, four bionic walking wheels (herringbone wheel, in-line wheel, V-shaped wheel and combination wheel) were designed and tested by imitating the structure and posture of ostrich’s feet travelling on sand. The results showed that when the wheel load was 20, 30 and 50N respectively and the slip ratio was less than 35%, the herringbone wheel had better traction trafficability than that of other wheels. When the wheel load was 30, 50 and 70N and the slip ratio was more than 35%, the in-line wheel had better performance than that of other wheels. It was shown in this thesis that the bionic walking wheels designed with the multi-posture wheel-legs and the simple structure could reduce the soil resistance and the disturbance to sand, thereby achieving a superior performance of traveling on sand. In addition, a new idea and research method for designing of walking mechanism on soft terrain has been provided in this thesis.