馬鈴薯播種機(jī)的性能評(píng)估@中英文翻譯@外文翻譯

Biosystems Engineering (2006) 95(1), 3541doi:10.1016/j.biosystemseng.2006.06.007PMPower and MachineryStrasseopening for dropping the potato into a furrow in thesoil.planters are equipped with two parallel rows of cupsper belt instead of one. Doubling the cup row allowsARTICLE IN PRESSparameters of machine performance. High accuracy ofplant spacing results in high yield and a uniform sortingand thus, a higher capacity at the same accuracy isexpected.Capacity and accuracy of plant spacing are the main double the travel speed without increasing the belt speed1537-5110/$32.00 35 r 2006 IAgrE. All rights reservedThe functioning of most potato planters is based on transport and placement of the seed potatoes by a cup-belt. The capacity of this process is rather low when planting accuracy has to stay at acceptable levels. Themain limitations are set by the speed of the cup-belt and the number and positioning of the cups. It washypothesised that the inaccuracy in planting distance, that is the deviation from uniform planting distances,mainly is created by the construction of the cup-belt planter.To determine the origin of the deviations in uniformity of placement of the potatoes a theoretical model wasbuilt. The model calculates the time interval between each successive potato touching the ground. Referring tothe results of the model, two hypotheses were posed, one with respect to the effect of belt speed, and one withrespect to the influence of potato shape. A planter unit was installed in a laboratory to test these twohypotheses. A high-speed camera was used to measure the time interval between each successive potato justbefore they reach the soil surface and to visualise the behaviour of the potato.The results showed that: (a) the higher the speed of the cup-belt, the more uniform is the deposition of thepotatoes; and (b) a more regular potato shape did not result in a higher planting accuracy.Major improvements can be achieved by reducing the opening time at the bottom of the duct and byimproving the design of the cups and its position relative to the duct. This will allow more room for changes inthe cup-belt speeds while keeping a high planting accuracy.r 2006 IAgrE. All rights reservedPublished by Elsevier Ltd1. IntroductionThe cup-belt planter (Fig. 1) is the most commonlyused machine to plant potatoes. The seed potatoes aretransferred from a hopper to the conveyor belt with cupssized to hold one tuber. This belt moves upwards to liftthe potatoes out of the hopper and turns over the uppersheave. At this point, the potatoes fall on the back of thenext cup and are confined in a sheet-metal duct. Atthe bottom, the belt turns over the roller, creating theof the tubers at harvest (McPhee et al., 1996; Pavek &Thornton, 2003). Field measurements (unpublisheddata) of planting distance in The Netherlands revealeda coefficient of variation (CV) of around 20%. Earlierstudies in Canada and the USA showed even higher CVsof up to 69% (Misener, 1982; Entz & LaCroix, 1983;Sieczka et al., 1986), indicating that the accuracy is lowcompared to precision planters for beet or maize.Travelling speed and accuracy of planting show aninverse correlation. Therefore, the present cup-beltAssessment of the Behaviour ofH. Buitenwerf1,2; W.B. Hoogmoed1Farm Technology Group, Wageningen University, P.Oe-mail of corresponding author:2Krone GmbH, Heinrich-Krone3IB-Lerink, Laan van Moerkerken 85, 3271AJ4Institute of Agricultural Engineering, University(Received 27 May 2005; accepted in revised formPotatoes in a Cup-belt Planter1; P. Lerink3;J.Mu ller1,4Box. 17, 6700 AA Wageningen, The Netherlands;willem.hoogmoedwur.nl10, 48480 Spelle, GermanyMijnsheerenland, The Netherlandsof Hohenheim, D-70593 Stuttgart, Germany20 June 2006; published online 2 August 2006)Published by Elsevier Ltdfor handling and transporting. Many shape features,usually combined with size measurements, can bedistinguished (Du & Sun, 2004; Tao et al., 1995; Zo dler,1969). In the Netherlands grading of potatoes is mostlydone by using the square mesh size (Koning de et al.,1994), which is determined only by the width and height(largest and least breadth) of the potato. For thetransport processes inside the planter, the length of thepotato is a decisive factor as well.ARTICLE IN PRESSH. BUITENWERF ET AL.36The objective of this study was to investigate thereasons for the low accuracy of cup-belt planters and touse this knowledge to derive recommendations fordesign modifications, e.g. in belt speeds or shape and78910Fig. 1. Working components of the cup-belt planter: (1)potatoes in hopper; (2) cup-belt; (3) cup; (4) upper sheave;(5) duct; (6) potato on back of cup; (7) furrower; (8) roller;(9) release opening; (10) ground level564321number of cups.For better understanding, a model was developed,describing the potato movement from the moment thepotato enters the duct up to the moment it touches theground. Thus, the behaviour of the potato at the bottomof the soil furrow was not taken into account. Asphysical properties strongly influence the efficiency ofagricultural equipment (Kutzbach, 1989), the shape ofthe potatoes was also considered in the model.Two null hypotheses were formulated: (1) the plantingaccuracy is not related to the speed of the cup-belt; and(2) the planting accuracy is not related to the dimensions(expressed by a shape factor) of the potatoes. Thehypotheses were tested both theoretically with the modeland empirically in the laboratory.2. Materials and methods2.1. Plant materialSeed potatoes of the cultivars (cv.) Sante, Arinda andMarfona have been used for testing the cup-belt planter,because they show different shape characteristics. Theshape of the potato tuber is an important characteristicThe field speed and cup-belt speed can be set toachieve the aimed plant spacing. The frequency f ofpotpotatoes leaving the duct at the bottom is calculated asfpotvcxc(2)where vcis the cup-belt speed in msC01and xcis thedistance in m between the cups on the belt. The angularspeed of the roller orin rad sC01with radius rrin m iscalculated asorvcrr(3)Table 1Shape characteristics of potato cultivars and golf balls used inthe experimentsCultivar Square mesh size, mm Shape factorSante 2835 146Arinda 3545 362Marfona 3545 168Golf balls 42C18 100A shape factor S based on all three dimensions wasintroduced:S 100l2wh(1)where l is the length, w the width and h the height of thepotato in mm, with howol. As a reference, alsospherical golf balls (with about the same density aspotatoes), representing a shape factor S of 100 wereused. Shape characteristics of the potatoes used in thisstudy are given in Table 1.2.2. Mathematical model of the processA mathematical model was built to predict plantingaccuracy and planting capacity of the cup-belt planter.The model took into consideration radius and speed ofthe roller, the dimensions and spacing of the cups, theirpositioning with respect to the duct wall and the heightof the planter above the soil surface (Fig. 2). It wasassumed that the potatoes did not move relative to thecup or rotate during their downward movement.The time of free fall tfallin s is calculated withARTICLE IN PRESSASSESSMENT OF THE BEHAVIOUR OF POTATOES 37The gap in the duct has to be large enough for a potatoxclearrcafii9825releaseafii9853xreleaseLine ALine CFig. 2. Process simulated by model, simulation starting when thecup crosses line A; release time represents time needed to createan opening sufficiently large for a potato to pass; model alsocalculates time between release of the potato and the moment itreaches the soil surface (free fall); rc, sum of the radius of theroller, thickness of the belt and length of the cup; xclear,clearance between cup and duct wall; xrelease, release clearance;arelease, release angle ; o, angular speed of roller; line C, groundlevel, end of simulationto pass and be released. This gap xreleasein m is reachedat a certain angle areleasein rad of a cup passing theroller. This release angle arelease(Fig. 2) is calculated ascos areleasercxclearC0xreleaserc(4)where: rcis the sum in m of the radius of the roller, thethickness of the belt and the length of the cup; and xclearis the clearance in m between the tip of the cup and thewall of the duct.When the parameters of the potatoes are known, theangle required for releasing a potato can be calculated.Apart from its shape and size, the position of the potatoon the back of the cup is determinative. Therefore, themodel distinguishes two positions: (a) minimum re-quired gap, equal to the height of a potato; and (b)maximum required gap equal to the length of a potato.The time treleasein s needed to form a release angle aois calculated astreleaseareleaseor(5)Calculating treleasefor different potatoes and possiblepositions on the cup yields the deviation from theaverage time interval between consecutive potatoes.Combined with the duration of the free fall and the fieldspeed of the planter, this gives the planting accuracy.yrelease vendtfall0C15gt2fall(8)where g is the gravitational acceleration (9C18msC02) andthe final velocity vendis calculated asvend v02gyrelease(9)with v0in msC01being the vertical downward speed ofthe potato at the moment of release.The time for the potato to move from Line A to therelease point treleasehas to be added to tfall.The model calculates the time interval between twoconsecutive potatoes that may be positioned in differentways on the cups. The largest deviations in intervals willoccur when a potato positioned lengthwise is followedby one positioned heightwise, and vice versa.2.3. The laboratory arrangementA standard planter unit (Miedema Hassia SL 4(6)was modified by replacing part of the bottom end of thesheet metal duct with similarly shaped transparentacrylic material (Fig. 3). The cup-belt was driven viathe roller (8 in Fig. 1), by a variable speed electric motor.The speed was measured with an infrared revolutionmeter. Only one row of cups was observed in thisarrangement.A high-speed video camera (SpeedCam Pro, Wein-berger AG, Dietikon, Switzerland) was used to visualisethe behaviour of the potatoes in the transparent ductand to measure the time interval between consecutivepotatoes. A sheet with a coordinate system was placedbehind the opening of the duct, the X axis representingthe ground level. Time was registered when the midpointof a potato passed the ground line. Standard deviationWhen the potato is released, it falls towards the soilsurface. As each potato is released on a unique angularposition, it also has a unique height above the soilsurface at that moment (Fig. 2). A small potato will bereleased earlier and thus at a higher point than a largeone.The model calculates the velocity of the potato justbefore it hits the soil surface uendin msC01. The initialvertical velocity of the potato u0inmsC01is assumed toequal the vertical component of the track speed of thetip of the cup:v0 rcorcosarelease(6)The release height yreleasein m is calculated asyrelease yrC0rcsinarelease(7)where yrin m is the distance between the centre of theroller (line A in Fig. 2) and the soil surface.ARTICLE IN PRESSH. BUITENWERF ET AL.38of the time interval between consecutive potatoes wasused as measure for plant spacing accuracy.For the measurements the camera system was set to arecording rate of 1000 frames per second. With anaverage free fall velocity of 2C15msC01, the potato movesapprox. 2C15mm between two frames, sufficiently smallto allow an accurate placement registration.The feeding rates for the test of the effect of the speedof the belt were set at 300, 400 and 500 potatoes minC01(fpot 5, 6C17 and 8C13sC01) corresponding to belt speedsof 0C133, 0C145 and 0C156msC01. These speeds would betypical for belts with 3, 2 and 1 rows of cups,respectively. A fixed feeding rate of 400 potatoes minC01(cup-belt speed of 0C145msC01) was used to assess theeffect of the potato shape.For the assessment of a normal distribution of thetime intervals, 30 potatoes in five repetitions were used.In the other tests, 20 potatoes in three repetitions wereused.Fig. 3. Laboratory test-rig; lower rightpart of the bottom end ofupper rightsegment faced2.4. Statistical analysisThe hypotheses were tested using the Fisher test, asanalysis showed that populations were normally dis-tributed. The one-sided upper tail Fisher test was usedand a was set to 5% representing the probability of atype 1 error, where a true null hypothesis is incorrectlyrejected. The confidence interval is equal to (100C0a)%.3. Results and discussion3.1. Cup-belt speed3.1.1. Empirical resultsThe measured time intervals between consecutivepotatoes touching ground showed a normal distribution.Standard deviations s for feeding rates 300, 400 and 500potatoes minC01were 33C10, 20C15 and 12C17ms, respectively.the sheet metal duct was replaced with transparent acrylic sheet;by the high-speed cameraAccording to the F-test the differences between feedingrates were significant. The normal distributions for allthree feeding rates are shown in Fig. 4. The accuracy ofthe planter is increasing with the cup-belt speed, withCVs of 8C16%, 7C11% and 5C15%, respectively.3.1.2. Results predicted by the modelFigure 5 shows the effect of the belt speed on the timeneeded to create a certain opening. A linear relationshipwas found between cup-belt speed and the accuracy ofthe deposition of the potatoes expressed as deviationfrom the time interval. The shorter the time needed forcreating the opening, the smaller the deviations. Resultsof these calculations are given in Table 2.The speed of the cup turning away from the duct wallis important. Instead of a higher belt speed, an increaseof the cups circumferential speed can be achieved bydecreasing the radius of the roller. The radius of theroller used in the test is 0C1055m, typical for theseplanters. It was calculated what the radius of the rollerhad to be for lower belt speeds, in order to reach thesame circumferential speed of the tip of the cup as foundfor the highest belt speed. This resulted in a radius of0C1025m for 300 potatoes minC01and of 0C1041m for 400potatoes minC01. Compared to this outcome, a lineartrend line based on the results of the laboratorymeasurements predicts a maximum performance at aradius of around 0C1020m.The mathematical model Eqn (5) predicted a linearrelationship between the radius of the roller (forr40C101m) and the accuracy of the deposition of thepotatoes. The model was used to estimate standarddeviations for different radii at a feeding rate of 300potatoes minC01. The results are given in Fig. 6, showingthat the model predicts a more gradual decrease inaccuracy in comparison with the measured data. Aradius of 0C1025m, which is probably the smallest radiustechnically possible, should have given a decrease inARTICLE IN PRESS0.0350.030f (x)0.0250.0200.0150.0100.0050.000180 260 500340Time x, ms420500 pot min1400 pot min1300 pot min1Standard deviation, ms1510500.00 0.02 0.04Radius lower roller, m0.06 0.08y = 922.1 x 17.597R2= 0.9995Fig. 6. Relationship between the radius of the roller and thestandard deviation of the time interval of deposition of thepotatoes; the relationship is linear for radii r40C101 m, K,measurement data; m, data from mathematical model; ,extended for ro0C101 m; , linear relationship; R2, coefficient ofdeterminationASSESSMENT OF THE BEHAVIOUR OF POTATOES 39Fig. 4. Normal distribution of the time interval (x, in ms) ofdeposition of the potatoes (pot) for three feeding rates806448Size of opening, mm321600.00 0.05 0.10 0.15Time, s0.20 0.250.36 m s10.72 m s10.24 m s1Fig. 5. Effect of belt speed on time needed to create openingTable 2Time intervals between consecutive potatoes calculated by themodel (cv. Marfona)Belt speed,msC01Difference between shortest and longestinterval, s0C172 17C160C136 29C140C124 42C1835302520y = 262.21 x 15.497R2= 0.9987standard deviation of about 75% compared to theoriginal radius.3.2. Dimension and shape of the potatoesThe results of the laboratory tests are given in Table 3.It shows the standard deviations of the time interval at afixed feeding rate of 400 potatoes minC01. These resultswere contrary to the expectations that higher standarddeviations would be found with increasing shape factors.Especially the poor results of the balls were amazing.The standard deviation of the balls was about 50%higher than the oblong potatoes of cv. Arinda. Thenormal distribution of the time intervals is shown inFig. 7. Significant differences were found between theballs and the potatoes. No significant differences werefound between the two potato varieties.The poor performance of the balls was caused by thefact that these balls could be positioned in many wayson the back of the cup. Thus, different positions of theballs in adjacent cups resulted in a lower accuracy ofdeposition. The three-dimensional drawing of the cup-belt shows the shape of the gap between cup andduct illustrating that different opening sizes are possible(Fig. 8).and the potatoes, demonstrated that the potatoes of cv.The mathematical model predicted the performanceof the process under different circumstances. The modelsimulated a better performance for spherical ballscompared to potatoes whereas the laboratory testshowed the opposite. An additional laboratory testwas done to check the reliability of the model.In the model, the time interval between two potatoesis calculated. Starting point is the moment the potatocrosses line A and end point is the crossing of line C(Fig. 2). In the laboratory test-rig the time-intervalbetween potatoes moving from line A to C wasmeasured (Fig. 3). The length, width and height of eachpotato was measured and potatoes were numbered.During the measurement it was determined how eachpotato was positioned on the cup. This position and thepotato dimensions were used as input for the model. Themeasurements were done at a feeding rate of 400potatoes minC0