Investigations on power requirement of active-passive combination tillage implement

Engineering in Agriculture, Environment and Food xxx (2016) 1e10

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Research paper

Investigations on power requirement of active-passive combination tillage implement Anpat Rahul Machindra, Hifjur Raheman* Agricultural and Food Engineering Department, IIT, Kharagpur, West Bengal 721302, India

a r t i c l e i n f o

a b s t r a c t

Article history: Received 30 January 2016 Received in revised form 11 May 2016 Accepted 27 June 2016 Available online xxx

In the present study, laboratory experiments were carried out to measure the draft and torque requirements of combination tillage implement (cultivator in the front set and rotavator in the rear set) by varying soil cone indices, peripheral to forward speed ratios (u/v) and depth ratios for a cutting width of 0.41 m and 0.65 m under controlled conditions in a soil bin with sandy clay loam soil at an average moisture content of 10.5 ± 1.2% (dry basis). Individual implements (cultivator and rotavator) of cutting widths of 0.41 and 0.65 m were also operated under similar conditions. Using non linear regression analysis, equations were developed for predicting draft, torque and power requirement of combination tillage implement. The maximum absolute difference between observed and predicted values of power requirement of the implement was found to be 12.43%. Power requirement of the implement was 43.93 and 33.17% lesser than the combined power requirement of individual implements for cutting widths of 0.41 and 0.65 m, respectively. With increase in width of tillage implements, power requirement increases directly due to increase in volume of soil handled. However, with increase in u/v ratio, power requirement decreases due to lesser time the rotavator is in contact with soil. Hence, to reduce the total power requirement of an active passive combination tillage implement, it is better to operate at higher u/v ratio and lesser depth ratio. © 2016 Asian Agricultural and Biological Engineering Association. Published by Elsevier B.V. All rights reserved.

Keywords: Combination tillage implement Depth ratio Peripheral to forward speed ratio Torque Draft Power requirement

1. Introduction The energy use in field preparation is of great concern for scientists and farmers. Among all field operations, conventional tillage requires highest amount of energy input. It requires several passes of various soil-turning and soil-pulverizing equipments requiring more time, fuel and labour. Moreover several passes of tractor with tillage implement increase soil compaction (Classen, 1996). In order to overcome these difficulties, one has to reduce the number of passes required to prepare the seedbed without sacrificing the quality of work. This is possible by combining tillage implements to be operated simultaneously (Sahu and Raheman, 2006). The combination tillage implement comprises combination of either active and passive or passive and passive tillage implements. In case of passive implements, power losses are more at tire-soil interface and also a considerable weight is required on drive

* Corresponding author. E-mail addresses: [email protected] (R.M. Anpat), [email protected]. in (H. Raheman).

wheels of tractor to provide necessary traction that results into detrimental soil compaction. Active tillage implements require considerable power per unit width as they till a greater volume of soil than is required in most field crop systems. Srivastava et al. (1993) stated that rotor develops a forward thrust resulting in a negative draft that may require further energy inputs to control tractor steering and three-point hitch and also may be harmful to the tractor drive train. A way to control this detrimental forward thrust is to combine active and passive elements that may result into following potential benefits: i) Power for tilling the soil can be transmitted to the tillage elements through a mechanical power train more efficiently than through the tire-soil interface. Hendrick (1980) estimated an overall average power transmission efficiency of 82% for PTO powered active tillage elements and 49% for drawbar passive tillage elements. ii) The negative draft of the active elements can be used to provide full or part of the draft of the passive elements and this will reduce draft of tillage tools and results in lesser wheel slip and

http://dx.doi.org/10.1016/j.eaef.2016.06.004 1881-8366/© 2016 Asian Agricultural and Biological Engineering Association. Published by Elsevier B.V. All rights reserved.

Please cite this article in press as: Anpat, R.M., Raheman, H., Investigations on power requirement of active-passive combination tillage implement, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.06.004

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R.M. Anpat, H. Raheman / Engineering in Agriculture, Environment and Food xxx (2016) 1e10

improved field productivity and allow the use of lighter tractors to reduce soil compaction. Reduced draft of tillage tools will also allow operations to be performed in more difficult traction conditions requiring the use of extra ballast, dual tires or assistance from the front wheels (Shinners et al., 1990). Chamen et al. (1979) developed and tested PTO driven rotary digger consisting of a rotary unit with L-shaped blades and deep chisel tines, mounted behind the rotary unit. They concluded that net energy requirement of rotary digger was 50% lesser than the conventional plough under similar operating conditions. Wilkes and Addai (1988) built and tested Wye double digger which consisted of a rotary subsoiler and an adjacent mould board bottom which turned next furrow onto the loosened subsoil. This digger reduced drawbar power, wheel slip and specific energy compared to mould board plough under similar operating conditions. Shinners et al. (1990, 1993) developed two combination tillage machines. The first machine had two active and two passive sets and the second machine consisted of an active rotary powered tillage set with conventional passive chisel tines. It was reported that combination machines required less draft and drawbar power than similar machines using purely passive tillage tools although total power consumption was same. The combination machines were more energy efficient than similar passive tillage tools. Weise (1993) performed experiments with combined arrangements of wing tines and a rotor with tines. He reported that pre-loosening of soil reduces the power requirement of following rotor. Manian et al. (1999) also reported that the energy, time and cost of operation for a combination tillage tool consisting of 16 tine rotary tiller and 2 to 4 chisel plow were reduced by 64.7e71.3%, 61.7e69.9% and 62.2e70.3%, respectively as compared to the combination of different implements when operated separately to obtain almost the same quality of tilth in black clay loam soil. A few more researchers (Kumar and Manian, 1986; and Kailappan et al., 2001a; 2001b) also combined active and passive units and reported saving in time and cost as compared to the conventional tillage practice. However, information on draft and torque requirements of combination tillage implements is very limited. The draft and torque requirement of tillage implement plays a vital role in developing more efficient tillage systems by matching the tractor with implement. Keeping the above points in view, the present study was undertaken to measure draft and torque requirement of activepassive combination tillage implement at different soil, implement and operating parameters in the laboratory condition, to develop an equation for predicting the power requirement for the implement, to compare the power requirement of combination tillage implement with respective individual tillage implement and to identify the parameter responsible for minimizing the power requirement.

where, AC is specific work of combination tillage implement (N/m2), AP and AA are specific work of passive set and active set operating as individual implement, respectively (N/m2). lP and lA are fractions of specific draft of passive and active implement acting as individual implement, respectively. These fractions values are always less than unity. AC can also be written as summation of specific work of combination tillage implement resulting from pulling resistance, AR (N/m2) and specific work of combination tillage implement resulting from torque, AT (N/m2). AC ¼ AR þ AT

(2)

Draft of the combination tillage implement, DC amounts to DC ¼ DP þ DX

(3)

where DP is draft (N) of passive set and DX is horizontal component of peripheral force (N) acting on the shaft of active set (Fig. 1). In order to have a considerably lower draft of combination tillage implement than similar type of passive implements, active sets with concurrent revolutions are used in the combination tillage implement. Neglecting the specific work of active set AC which results from the action of the component force DX pushing the machine and comparing equations (1) and (2), the following equations could be obtain

lP AP ¼ AR

(4)

lA AA ¼ AT

(5)

Individual specific works are calculated according to the formulas

AP ¼

DP aP bP

(6)

AR ¼

DC aC bC

(7)

AA ¼

2pTA a A bA lg

(8)

AT ¼

2pTC aC bC lg

(9)

where a, b stand for depth and width of implement, respectively. D, T stand for draft (N) and torque (Nm), respectively. lg is the travel length (m) covered by the machine at one full revolution of the shaft of the active set which is given as

2. Materials and methods 2.1. Approach for prediction of power requirement of combination tillage implement Based on theoretical approach on active-passive combination tillage implement proposed by Bernacki et al. (1972), a study on modelling power requirement of an active-passive combination tillage implement was carried out. The specific work of a combination tillage implement consists of specific work of passive set and active set which can be expressed as AC ¼ lP AP þ lA AA

(1)

lg ¼

2pV

(10)

u

where, V is forward velocity of implement (m/s) and u is angular speed of rotavator shaft (rad/s). By comparing equations (4) (6) and (7), coefficient lP could be calculated as

lP ¼

AR ¼ AP



DC a C bC



aP bP DP

 (11)

By comparing equations (5) (8) and (9), coefficient lA could be calculated as

Please cite this article in press as: Anpat, R.M., Raheman, H., Investigations on power requirement of active-passive combination tillage implement, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.06.004

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3

Fig. 1. Schematic diagram of combination tillage implement (cultivator and rotavator) tested.

lA ¼

AT ¼ AA



TC aC bC



aA bA TA

(16), PP and PA are given as

 (12)

Considering aC ¼ aP and bC ¼ bP ¼ bA in equations (11) and (12)

lP ¼ lA ¼

DC DP 

TC TA

(13) 

aA aC

(17)

PA ¼ AA aA bA v

(18)

By using equations (10) and (18) PA ¼ TA u

 (14)

Power requirement of combination tillage implement,

¼ ðlP AP aC bC VÞ þ ðlA AA aC bC vÞ ¼ ðlP AP aP bP VÞ þ ðlA AA aA bA VÞ



aC aA

(19)

From equations (13)e(14), (16)e(17) and (19), PC can also be given as PC ¼ (DC v) þ (TC u)

PC ¼ AC ðaC bC vÞ ¼ ðlP AP þ lA AA ÞðaC bC vÞ

  a PC ¼ ðlP PP Þ þ ðlA PA Þ C aA

PP ¼ AP aP bP v ¼ DP v

(20)

 (15)

(16)

where, v is forward velocity of combination tillage implement. PP and PA are power requirement of passive and active sets operating as individual implement, respectively. From equations (15) and

2.2. Experimental procedure The experimental procedure followed to evaluate the performance of combination tillage implement in terms of draft and torque requirement in a soil bin at different soil cone indices, operating and implement parameters is as discussed below.

Fig. 2. Soil bin facility a) soil processing trolley b) implement trolley c) cultivator d) rotavator.

Please cite this article in press as: Anpat, R.M., Raheman, H., Investigations on power requirement of active-passive combination tillage implement, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.06.004

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R.M. Anpat, H. Raheman / Engineering in Agriculture, Environment and Food xxx (2016) 1e10 Table 1 Experimental plan (variable levels) for soil bin experiments. Variables

Levels

Independent variables Width, m Depth ratio (depth of rotavator, m) u/v ratio (forward speed, km/h) Cone index, kPa Dependent variables Draft Torque

2 3 4 3

Fig. 3. A sample plot of variation of cone index with depth of soil.

2.2.1. Soil bin A stationary soil bin of length 15.0 m, width 1.8 m and depth 0.6 m deep comprised a carriage system, implement and soil processing trolleys, a power transmission system, a control unit and instrumentation (Fig. 2). The bin was provided with two rails, one on top of each side of the bin wall, were used for supporting the soil processing and the implement trolleys. The soil processing trolley comprised a frame, rotary tiller, leveling blade and roller to till, level and compact the soil, respectively to obtain the desired cone index (Table 1). A sprayer was used to apply water on the soil to maintain the desired average moisture content of 10.5 ± 1.2% (dry basis) with a liquid limit of 17.1% and plastic limit of 12.05%. The different speeds of operation were obtained by choosing suitable gears of a gear reduction unit coupled to the input shaft of the revolving drum, which was attached to the soil processing trolley with stainless steel rope. A control unit, placed outside the soil bin, controlled the direction of movement of the soil processing trolley. 2.2.2. Soil bed preparation in the soil bin The experiments were conducted using sandy clay loam soil at an average moisture content of 10.5 ± 1.2% (dry basis). This moisture content was chosen to coincide with the normal moisture level

0.41 and 0.65 1.2 (0.1), 1.5 (0.08) and 2 (0.06) 4.95 (3.2), 7.20 (2.2), 13.20 (1.2), 19.78 (0.8) 500 ± 50, 700 ± 50 and 900 ± 50 For cultivator, rotavator and combination tillage implement For rotavator and combination tillage implement

at which tillage operations are generally carried out in the field. Before conducting the experiments, the soil bed was prepared to achieve the desired levels of cone index. At first, the tiller was used to pulverize the soil after that water was sprayed as desired. Then, the soil was levelled with the levelling blade and compacted by the roller to the desired cone penetration resistance in layers. At the end of each soil preparation, a hydraulically operated soil cone penetrometer with a base area of 3.22 cm2 was used to measure the cone penetration resistance to a depth of 0.15 m at intervals of 0.025 m at three locations in the soil bin following the procedures outlined in the ASABE Standards (ASAE Standard, 2000). These locations were 2 m apart along the centre of the bin and were selected to check the soil condition near the start of the soil bed, in the middle and towards the end. To ensure soil uniformity, soil bed preparation was repeated if the cone penetration resistance varied significantly from the desired values (Table 1). A sample plot for variation of cone index values with depth of soil in the oil bin is shown in Fig. 3. 2.2.3. Laboratory set up for measuring power requirement of combination tillage implement A set up was developed for measuring power requirement of active-passive combination tillage implement with cultivator in front passive set and rotavator in rear active set (Fig. 4). Cultivator and rotavator were mounted on two separate frames. Width of cultivator was varied from 0.41 m to 0.65 m by adding tines and varying spacing between them. Rotavator had operating width of 0.65 m and width corresponding to 0.41 m cultivator was obtained by removing C shaped blades arranged in axial pattern on shaft from both ends equally. Cultivator’s operating depth was kept constant as 0.12 m and depth of operation of rotavator was varied manually by screw and jack arrangement to get different passiveeactive depth ratios (1.25, 1.5 and 2). Drive to the rotavator shaft was taken from a 5.6 kW induction motor through chain drive in two stages with a total speed reduction of 6.67. The ratio of peripheral speed of rotor blade to forward velocity of the implement (u/v) was varied by varying the forward velocity (v) and keeping the rotavator shaft rpm constant as 220 rpm (peripheral speed, u as 15.83 km/h).

Fig. 4. a. Flats with strain gauges for measuring draft of implements. b. Torque transducer mounted on motor shaft.

Please cite this article in press as: Anpat, R.M., Raheman, H., Investigations on power requirement of active-passive combination tillage implement, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.06.004

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1.2

1.5

1600

2

400

1.5

2

800 400 0

0 0

5

10

15

20

u/v ratio

0

25

(i) Cone index 500± 50 kPa 1200

1.2

1.5

5

10

15

20

u/v ratio

25

(i) Cone index 500± 50 kPa 1600

2

1.2

1.5

2

1200

Draft, N

800

Draft, N

1.2

1200

800

Draft, N

Draft, N

1200

5

400

800 400

0 0

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0

u/v ratio

0

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u/v ratio (ii) Cone index 700± 50 kPa 1600

1.2

1.5

(ii) Cone index 700± 50 kPa 2000

2

Draft, N

1200

Draft, N

1.2

1.5

2

1600 1200

800 400

800 400

0 0

5

10

15

20

25

u/v ratio (iii) Cone index 900± 50 kPa (a) 0.41 m width

0 0

5

10

15

20

25

u/v ratio (iii) Cone index 900± 50 kPa (b) 0.65 m width

Fig. 5. Variation of draft of combination tillage implement when operated at different operating and soil parameters.

2.2.4. Instrumentation and measurements Measurement of speed of implement was carried out with a proximity switch, attached to the soil processing trolley and steel rods fixed at 0.5 m apart along the side of the rail provided on the soil bin and each with a projection of 0.07 m. Depth of operation of cultivator was recorded with potentiometer and rack and pinion arrangement mounted on the implement trolley. Cultivator was raised and lowered with the help of a hydraulic system and corresponding readings of depth were recorded in data acquisition system. Rotavator was raised and lowered manually by a screw and jack arrangement and its depth of operation was measured with the help of a scale. The draft requirement of combination tillage implement was measured by fixing strain gauges on a flat link connecting soil processing trolley with implement trolley as shown in Fig. 4a. Torque requirement of rotavator was measured with a torque transducer which was coupled to the output shaft of 5.6 kW 3 phase induction motor as shown in Fig. 4b.

2.2.5. Test procedure Before each test, the soil bed was prepared using the soil processing trolley as discussed in section 2.2.2. Each test was carried out for a test length of 5 m in the middle span of the prepared soil bed and was replicated thrice. After selecting a gear to obtain the desired speed and fixing the desired depth of operation for the implement, it was pulled through soil. With the help of calibrated strain gauges attached to the flats placed in between soil processing trolley and implement trolley, torque transducer and proximity switch, the data on draft, torque and speed of operation were continuously acquired in the data acquisition system (DAS). At the end of each test, the soil bed was disturbed and was prepared again following the same procedure to conduct other tests. 2.2.6. Experimental layout Experiments were conducted in the laboratory for activepassive combination tillage implement and also for individual

Please cite this article in press as: Anpat, R.M., Raheman, H., Investigations on power requirement of active-passive combination tillage implement, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.06.004

6

R.M. Anpat, H. Raheman / Engineering in Agriculture, Environment and Food xxx (2016) 1e10 Table 2 ANOVA for draft of combination tillage implement. Source of variation

df

MS

Computed F value

Width Cone index u/v ratio Depth ratio Width  Cone index Width  u/v ratio Width  Depth ratio Cone index  u/v ratio Cone index  depth ratio u/v ratio  depth ratio Width  Cone index  u/v ratio Width  Cone index  depth ratio Width  u/v ratio  depth ratio Cone index  u/v ratio  depth ratio Width  Cone index  u/v ratio  depth ratio Error

1 2 3 2 2 3 2 6 4 6 6 4 6 12 12 72

3,027,000 2,110,000 455,100 1,103,000 51,259.29 12,626.60 16,632.90 6363.84 11,618.11 3676.63 12,838.37 6007.24 1364.61 5852.95 2932.65 4987.18

607.03** 423.13** 91.26** 221.22** 10.28* 2.53 3.34* 1.28 2.33 0.74 2.57* 1.20 0.27 1.17 0.59

df: degree of freedom; MS: mean square. ** Significant at 1% level. * Significant at 5% level.

tillage implements. The experimental plan for soil bin experiments is as given in Table 1. 2.2.7. Statistical analysis Statistical analysis was performed using the statistical software SPSS statistics 17.0. Analysis of variance (ANOVA) was carried out to evaluate the significance of impact of different independent variables and their interactions on magnitude of draft and torque requirement of combination tillage implement. Only significant variables were considered to develop the equations for predicting draft and torque requirement of combination tillage implement. Curve fitting was carried out to determine the relation between individual independent variable and dependent variable for highest value of coefficient of determination (R2) and this relation was used in final equation for predicting draft and torque requirement. Non linear regression analysis was performed to find out the final equation for predicting draft and torque requirement of combination tillage implement. 3. Results and discussion 3.1. Draft of combination tillage implement The combination tillage implement having widths 0.41 and 0.65 m were tested at three levels of soil compaction, four levels of u/v ratio and three different depth ratios. The corresponding draft values are plotted in Fig. 5. The analysis of variance (ANOVA) for the draft requirement of combination tillage implement is given in Table 2. From this table, it can be seen that the effects of all variables were highly significant on the draft of combination tillage implement. 3.1.1. Effect of u/v ratio In general, the draft of combination tillage implement increased with decrease in u/v ratio. From Fig. 5, it can be seen that increasing u/v ratio from 4.95 to 19.78, the draft of combination tillage implement decreased by 20.40e51.44%, 17.56e39.30% and 12.24e38.01% for cone index of 500, 700 and 900 kPa, respectively and for all values of width and depth ratio. With increase in u/v ratio, forward speed decreased, hence, the draft of combination tillage implement decreased. This was because of the higher force required to accomplish the soil acceleration with increase in speed of operation (Sahu and Raheman, 2006) and also pushing force

developed by rotavator decreased with decrease in u/v ratio in magnitude because of longer bite sizes. Similar findings were also reported by Hendrick (1980) and Shinners et al. (1993). 3.1.2. Effect of depth ratio When depth ratio was increased from 1.2 to 2, the draft of combination tillage implement increased by 61.45e141.03%, 17.98e63.54% and 22.89e60.80% for cone index of 500, 700 and 900 kPa, respectively and for all values of width and u/v ratio (Fig. 5). The obvious explanation for this could be, with increase in depth ratio i.e. keeping the depth of cultivator constant and decreasing the depth of rotavator, decreased pushing force developed by rotavator. Similar findings were also reported by Shinners et al. (1993), Srivastava et al. (1993) and Marenya and Du Plessis (2006). 3.1.3. Effect of width When width of cut was increased from 0.41 m to 0.65 m, the draft of combination tillage implement increased by 20.81e56.98%, 19.63e39.46% and 16.87e45.13% for cone index of 500, 700 and 900 kPa, respectively and for all values of u/v ratio and depth ratio (Fig. 5). This could be due to more volume of soil handled with increase in width of cut. With increase in width, draft of cultivator increased more compared to the increase in pushing force developed by rotavator which resulted in increased draft of combination tillage implement. 3.1.4. Effect of soil cone index When the average soil cone index was increased from 500 to 900 kPa, draft of combination tillage implement increased by 55.78e153.12% and 34.82e98.44% for 0.41 m and 0.65 m widths, respectively and for all values of depth ratio and u/v ratio (Fig. 5). This could be due to higher soil resistance associated with higher cone index values. 3.2. Torque requirement of combination tillage implement The combination tillage implement having widths of 0.41 and 0.65 m were tested at three levels of soil compaction, four levels of u/v ratio and three different depth ratios. The corresponding torque values are plotted in Fig. 6. The results of ANOVA for the torque of combination tillage implement are given in Table 3. It can be seen from this table that the effects of width of implement, soil cone

Please cite this article in press as: Anpat, R.M., Raheman, H., Investigations on power requirement of active-passive combination tillage implement, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.06.004

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1.2

1.5

60

2

Torque, Nm

Torque, Nm

60

40

20

1.2

0

2

40

20

5

10

15

20

0

25

u/v ratio (i) Cone index 500± 50 kPa

5

1.5

40

20

0 0

5

10

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20

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25

1.5

2

40 20 0

25

0

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u/v ratio (ii) Cone index 700± 50 kPa

(ii) Cone index 700± 50 kPa 1.2

20

60

u/v ratio

80

15

u/v ratio

1.2

2

Torque, Nm

1.2

10

(i) Cone index 500± 50 kPa 80

60

Torque, Nm

1.5

0

0

80

2

60

1.2

1.5

2

60

Torque, Nm

Torque, Nm

7

40

20

40

20

0 0

5

10

15

20

25

u/v ratio (iii) Cone index 900± 50 kPa (a) 0.41 m width

0 0

5

10

15

u/ v ratio

20

25

(iii) Cone index 900± 50 kPa (b) 0.65 m width

Fig. 6. Variation of torque of combination tillage implement when operated at different operating and soil parameters.

index, depth ratio and u/v ratio were highly significant. However, effect of interactions of variables was less significant. 3.2.1. Effect of u/v ratio From Fig. 6, it can be seen that, increasing u/v ratio from 4.95 to 19.78, resulted 35.22e47.47%, 30.56e41.43% and 30.36e49.69% decrease in the torque requirement of combination tillage implement for cone index of 500, 700 and 900 kPa, respectively and for all values of width and depth ratio. One possible reason for this could be, with decrease in u/v ratio, each blade on rotavator shaft took a longer bite thus increasing the torque requirement. Similar findings were also reported by Ghosh (1967), Hendrick (1980) and Shinners et al. (1993). 3.2.2. Effect of depth ratio From Fig. 6, it can be seen that increasing depth ratio of combination tillage implement from 1.2 to 2 decreased torque values by 17.43e34.26%, 10.06e42.86% and 15.62e49.12% for cone index of

500, 700 and 900 kPa, respectively and for all values of width and u/ v ratio. With increase in depth ratio, operating depth of rotavator decreased resulting in decreased tilling route length and decreased volume of soil processed by a blade at constant kinematic parameter. Similar findings were reported by Ghosh (1967), Shinners et al. (1993) and Marenya and Du Plessis (2006). 3.2.3. Effect of width When width of cut was increased from 0.41 m to 0.65 m, the torque requirement of combination tillage implement increased by 5.23e53.54%, 11.76e68.04% and 5.76e56.07% for soil cone index of 500, 700 and 900 kPa, respectively and for all values of u/v ratio and depth ratio (Fig. 6). It may be because of more volume of soil associated with increase in width of cut. 3.2.4. Effect of soil cone index From Fig. 6, it can be seen that when the average soil cone index was increased from 500 to 900 kPa, the torque of combination

Please cite this article in press as: Anpat, R.M., Raheman, H., Investigations on power requirement of active-passive combination tillage implement, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.06.004

8

R.M. Anpat, H. Raheman / Engineering in Agriculture, Environment and Food xxx (2016) 1e10 Table 3 ANOVA for torque of combination tillage implement. Source of variation

df

MS

Computed F value

Width Cone index u/v ratio Depth ratio Width  Cone index Width  u/v ratio Width  Depth ratio Cone index  u/v ratio Cone index  depth ratio u/v ratio  depth ratio Width  Cone index  u/v ratio Width  Cone index  depth ratio Width  u/v ratio  depth ratio Cone index  u/v ratio  depth ratio Width  Cone index  u/v ratio  depth ratio Error

1 2 3 2 2 3 2 6 4 6 6 4 6 12 12 72

858.47 1905.24 1956.74 1899.24 142.30 27.95 16.05 74.62 60.72 41.55 94.15 4.77 16.48 5.90 3.75 21.68

39.60** 87.88** 90.26** 87.61** 6.56* 1.29 0.74 3.44* 2.80* 1.92 4.34* 0.22 0.76 0.27 0.17

df: degree of freedom; MS: mean square. ** Significant at 1% level. * Significant at 5% level.

Fig. 7. a. Power requirement of cultivator, rotavator and combination tillage implement of 0.41 m width at different values of u/v ratio, soil cone index and depth ratio. b. Power requirement of cultivator, rotavator and combination tillage implement of 0.65 m width at different values of u/v ratio, soil cone index and depth ratio.

tillage implement increased by 55.78e153.12% and 34.82e98.44% for 0.41 m and 0.65 m widths, respectively and for all values of depth ratio and u/v ratio. This could be due to higher soil resistance associated with higher cone index values.

3.3. Comparison of power requirement of combination tillage implement with respective individual tillage implement Power requirements of cultivator, rotavator and combination

Please cite this article in press as: Anpat, R.M., Raheman, H., Investigations on power requirement of active-passive combination tillage implement, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.06.004

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3000

Value

Regression coefficient

Value

B0 B1 B2 B3 B4 R2

546.46 11.01 1.04 16.76 591.04 0.978

C0 C1 C2 C3 C4 R2

31.69 0.26 0.04 1.06 15.37 0.927

Predicted power, W

Table 4 Regression coefficients in equations predicting draft and torque of combination tillage implement. Regression coefficient

9

2500

Slope = 1

2000 1500

Slope = 1.04 R² = 0.98

1000 500 0

tillage implement were calculated by using Eqs. (17) (19) and (20), respectively. Comparison of power requirement of combination tillage implement with respective individual tillage implement is shown in Fig. 7a and b for cutting widths of 0.41 m and 0.65 m, respectively. It can be seen from these figures that the power requirement of combination tillage implement was lower than the sum of the power requirement of individual tillage implements. The per cent decrease in power requirement when using combination tillage implement instead of conventional tillage implement was 43.93 and 33.17% for 0.41 and 0.65 m cutting widths, respectively.

3.4. Development of equation for predicting power requirement of combination tillage implement In order to develop equations, interactions of variables were neglected as they did not have significant effect on draft and torque of combination tillage implement (Tables 2 and 3). Significant interactions were neglected as they increased complexity of model without improving much accuracy. All variables had linear relationship with draft and torque of the implement. However, depth ratio had logarithmic relationship with draft of the implement. By using SPSS software for non-linear regression analysis of data obtained from laboratory testing of combination tillage implement was carried out and values of coefficients (Eqs. (21) and (22)) were determined for best fit. High values of R2 in Table 4 indicate that the variables in Eqs. (21) and (22) can explain most of the variability in the experimental data.

0

500

1000 1500 Observed power, W

2000

2500

Fig. 8. Comparison of observed and predicted values of power requirement of combination tillage implement.

With increase in width of tillage implements, power requirement increases directly due to increase in volume of soil handled. However, with increase in u/v ratio, power requirement decreases due to lesser time the rotavator is in contact with undisturbed or virgin soil. Hence, to reduce the total power requirement of an active passive combination tillage implement, it is better to operate at higher u/v ratio and lesser depth ratio. Looking at the size of the field and the field capacity, the u/v ratio for active passive combination tillage implement should be around 7. 3.5. Validation of developed equation The developed equation for prediction of power requirement of combination tillage implement was verified against the data other than the ones from which this equation was developed. Out of the total data obtained 25% was used for validation of the developed equation. The observed and predicted values of power requirement of combination tillage implement were compared in Fig. 8. From this figure, it can be seen that the slope of best fitted line was 1.04. The maximum absolute difference between observed and predicted values of power was found to be 12.43%. In the view of the experimental errors incurred in the measurement of the power of combination tillage implement, this value was considered acceptable.

Draft, D ¼ B0 þ (B1  W) þ (B2  CI) e (B3  u/v) þ (B4  ln DR)(21) 4. Conclusions Torque, T ¼ C0 þ (C1  W) þ (C2  CI) e (C3  u/v) e (C4  DR)(22) where W is width (cm), CI is soil cone index (kPa), u/v is ratio of peripheral speed of rotavator shaft to forward speed, DR is depth ratio, Bi and Ci are regression coefficients whose values are given in Table 4 where i ¼ 0, 1, ., 4. According to the equation (20), discussed in section 2.1, total power requirement of combination tillage implement is given by PC ¼ (DC. V) þ (TC. u) Therefore by using equations for predicting draft and torque (equations (21) and (22)), power requirement of combination tillage implement is expressed as PC ¼ [(B0 þ (B1  W) þ (B2  CI) e (B3  u/v) þ (B4  ln DR)).V] þ [(C0 þ (C1  W) þ (C2  CI) e (C3  u/v) e (C4  DR)).u]

(23)

From Equation (23), it can be seen that power requirement of combination tillage implement for a given soil condition is a strong function of width of tillage implement, u/v ratio and depth ratio.

Based on the results of this study, the following specific conclusions were drawn:  Draft values of combination tillage implement increased with increase in depth ratio, soil cone index and width and decreased with increase in u/v ratio.  Torque requirement of combination tillage implement increased with increase in width and soil cone index values however it decreased with increase in u/v ratio and depth ratio.  In sandy clay loam soil, combination tillage implement of width 0.41 and 0.65 m outperformed the respective individual tillage implements in power requirement by 43.93% and 33.17%, respectively.  Using equations for predicting draft and torque obtained by non linear regression analysis, equation for predicting power requirement of combination tillage implement was developed. A small difference between the predicted and observed values of power requirement of combination tillage implement in sandy clay loam soil validated the developed prediction equation.  For a given soil condition, the width of implement, u/v ratio and depth ratio are the important parameters controlling total

Please cite this article in press as: Anpat, R.M., Raheman, H., Investigations on power requirement of active-passive combination tillage implement, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.06.004

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power requirement of combination tillage implement. Increasing width of the tillage implement helps to increase draft of implement, whereas, increasing u/v ratio and depth ratio help in decreasing both draft and torque requirement of implement. Hence, u/v ratio of around 7 (considering the limitation of land size and pto rpm; and higher field capacity) is recommended for an active passive combination tillage implement in any soil condition. References ASAE Standard, 2000. ASAE S313.3. Soil Cone Penetrometer. ASAE. ASAE, St. Joseph, Mich. Bernacki, H., Haman, J., Kanafojski, Cz, 1972. Agricultural Machines, Theory and Construction, vol. I. Scientific Publications Foreign Co-operation Centre of the CISTEI, Warsaw, Poland, pp. 429e439. Chamen, W.C.T., Cope, R.F., Patterson, D.E., 1979. Development and performance of a high output rotary digger. J. Agric. Eng. Res. 24 (4), 301e308. Classen, S.L., 1996. Mechanized Minimum and No-till Crop Production for Research Farms. IITA Research Guide, p. 11. Ghosh, B.N., 1967. The power requirement of rotary cultivator. J. Agric. Eng. Res. 12 (1), 5e12. Hendrick, J.G., 1980. A Powered rotary chisel. Trans. ASAE 23 (6), 1349e1352. Kailappan, R., Manian, R., Amuthan, G., Vijayaraghavan, N.C., Duraisamy, G., 2001a. Combination tillage tool - I (Design and development of a combination tillage

tool). Agric. Mech. Asia Afr. Lat. Am. 32 (3), 19e22. Kailappan, R., Swaminathan, H.R., Vijayaraghavan, N.C., Amuthan, G., 2001b. Combination tillage tool - II (Performance evaluation of the combination tillage tool under field conditions). Agric. Mech. Asia Afr. Lat. Am. 32 (4), 9e12. Kumar, V.J.F., Manian, R., 1986. Tractor-drawn combination tillage tool. Agric. Mech. Asia Afr. Lat. Am. 17 (1), 31e36. Manian, R., Nagaiyan, V., Kathirvel, K., 1999. Development and evaluation of combination tillage bed furrow-former. Agric. Mech. Asia Afr. Lat. Am. 30 (4), 22e29. Marenya, M.O., Du Plessis, H.L.M., 2006. Torque Requirement and Forces Generated by a Deep Tilling Down-cut Rotary Tiller. ASABE Paper No. 061096. ASAE, St Joseph, Mich. Sahu, R.K., Raheman, H., 2006. An approach for draft prediction of combination tillage implements in sandy clay loam soil. Soil Till. Res. 90 (1e2), 145e155. Shinners, K.J., Alcock, R., Wilkes, J.M., 1990. Combining active and passive tillage elements to reduce draft requirements. Trans. ASAE 33 (2), 400e404. Shinners, K.J., Wilkes, J.M., England, T.D., 1993. Performance characteristics of a tillage machine with active - passive components. J. Agric. Eng. Res. 55 (4), 277e297. Srivastava, A.K., Goering, C.E., Rohrbach, R.P., 1993. Engineering Principles of Agricultural Machines. ASAE Textbook No. 6. American society of agricultural Engineers, 2950 Niles Road, St. Joseph, Mich. ASAE. Weise, G., 1993. Active and passive elements of a combined tillage machine: interaction, draught requirement and energy consumption. J. Agric. Eng. Res. 56 (4), 287e299. Wilkes, R.D., Addai, S.H., 1988. The use of the ‘Wye Double Digger’ as an alternative to the plough to reduce energy requirement per hectare and soil damage. In: Presented at the International Conference of Agric. Eng. Paper No. 88e190.

Please cite this article in press as: Anpat, R.M., Raheman, H., Investigations on power requirement of active-passive combination tillage implement, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.06.004