Printer Friendly

Analysis of the coffee harvesting process using an electromagnetic shaker.

Introduction

The production chain of coffee is constituted by several operations, with harvest being the most expensive. A large labor contingent is necessary for harvesting. This operation also directly affects the final quality of coffee (PIMENTA; VILELA, 2003; CIRO, 2001). Prieto et al. (2008) affirmed that the concept of agricultural product quality has been changing during recent years and has been playing a fundamental role on the determination of agricultural product prices. Coffee is considered one of the products that consumer markets have been most demanding of high quality.

Engineers and researchers have been aware of mechanical fruit harvesting for five decades. This mechanization process is influenced by the variability of many factors; most important are the structure, form and size of the plants and characteristics of the fruits to be picked (SRIVASTAVA et al., 1996). In mechanical coffee harvesting, the main difficulties faced are the varying architectural characteristics of the plant and the nonuniformity of fruit ripeness (SOUZA et al., 2002).

Mechanical harvesting of coffee fruits has been accomplished by mechanical vibration. This principle of harvesting has been used to design machines for harvesting many types of fruits such as oranges, peaches and olives (ROSA et al., 2008; CASTRO-GARCIA et al., 2008; WHITNEY et al., 2001). However, under certain conditions this process does not present desirable efficiencies. In order to improve this process, knowledge of the dynamic behavior of the harvesting system is necessary. The dynamic characteristics, frequency and vibration amplitude stand out as the most important for system evaluation (SOUZA et al., 2002; SESSIZ; OZCAN, 2006).

Tascon et al. (2005) analyzed the coffee harvesting process using portable coffee branch vibrators and verified the viability of this type of equipment for coffee harvesting. The results showed that when using portable vibrators, harvesting performance was 341.7 to 458.3% greater than traditional manual harvesting. Ciro (2001) performed a study in which the natural frequencies of the coffee fruit-stem system were obtained by using a two-degrees-of-freedom theoretical model. The results showed the importance of dynamic behavior analysis of the systems to better understand the process of detaching fruit from the coffee plant.

For coffee harvester design, it is important to study the dynamic behavior of coffee fruits when submitted to mechanical vibrations. Electromagnetic vibrators have been used as an essential tool to study mechanical harvesting processes of other products (ROSA et al., 2008). The advantage of the use of this equipment type in relation to mechanical systems is that the frequency, amplitude and vibration time can be easily controlled. Therefore, electromagnetic vibrations seem to be the correct tool to analyze, understand and develop systems for coffee harvesting by vibration.

[FIGURE 1 OMITTED]

The objective of this work was to determine the effect of the frequency and amplitude of vibration on cherry coffee fruit detachment efficiency for the Catuai Vermelho and Mundo Novo varieties when using an electromagnetic shaker.

Material and methods

The work was developed in the Laboratory of Machine Design and Machine Vision (PROVISAGRO) of the Department of Agricultural Engineering at the Federal University of Vicosa.

For performance of the vibration tests, a device produced by LDS (Ling Dynamic Systems) was used. This system, presented in Figure 1, was composed of a COMETUSB signal generator made by Dactron, a PA100E-CE amplifier and a model V. 406 electromagnetic shaker made by LDS.

Through a specific program supplied by LDS, the COMETUSB signal generator produced a sinusoidal, random or impact signal, which was amplified by the PA100E-CE amplifier before reaching the shaker. For this work, sinusoidal signals were used since this type of signal better represents the common type of excitement produced by mechanical coffee harvesters.

The shaker works in a dynamic range of 5 Hz to 9 kHz, with a maximum load of 198 N. The maximum displacement of the movable base is 17.6 mm (peak-to-peak), with a maximum acceleration of 100 times the acceleration of gravity. Another important characteristic of the utilized system was that a metallic device was fitted to the shaker to hold the coffee branches during the vibration tests. The system used to perform the vibration tests is showed in Figure 2.

The employed system for attaching the coffee branch to the shaker is presented in Figure 3. This structure was composed of a rigid base, in which a holding device was adapted to keep the coffee branch linked to the shaker structure without damage. The holding device also allowed for changes in vibration direction, so transversal and longitudinal branch vibration tests were performed.

[FIGURE 2 OMITTED]

Figure 3a shows the piezoelectric acceleration sensor used to control the vibration process. Acceleration measured by this sensor was used by the system to control the frequency and amplitude of vibration of the shaker.

The electromagnetic shaker was used to perform the vibration tests. A completely randomized factorial design with three replications was used. In this experiment, the evaluated factors that affect the efficiency of cherry fruit detachment were frequency, amplitude and direction of vibration, and length of the branch, for the varieties Catuai Vermelho and Mundo Novo. In all tests the branches were submitted to 15 seconds of vibration. The levels of the studied factors used in this experiment are presented in Table 1.

The branches used in this experiment were collected randomly in an experimental area located at the Federal University of Vicosa campus. Afterwards, the branches were cut to different lengths, as presented in the Table 1.

[FIGURE 3 OMITTED]

Detachment efficiency was calculated by dividing the number of removed ripe fruits per total number of ripe fruits presented on the branch before being submitted to vibration.

The obtained efficiency of fruit detachment data in this experiment were, initially, submitted to analysis of variance at a 5% significance level. The effect of the frequency and amplitude of vibration factors were studied by regression analysis; the models were chosen based on the determination coefficient and the significance of the regression coefficients, using the t-test under 1% of probability. All of the statistical analyses were performed using SAS software, version 8.0.

Results and discussion

In Tables 2 and 3, the results of the analyses of variance are presented for coffee fruit detachment efficiency obtained for branches collected from plants of the Mundo Novo and Catuai Vermelho varieties, respectively.

According to the results presented in Table 2, it was verified that for the Catuai Vermelho variety, only the interaction between the frequency and amplitude factors was significant at the level of 5%. For the Mundo Novo variety, the interaction between the frequency and amplitude of vibration factors (F x A), between frequency and branch length (F x C) and between branch length and direction of vibration factor (C x D) were significant, as shown in Table 3.

Considering that the interaction between frequency and amplitude of vibration was significant for each studied variety, a study of those factors through regression analysis was performed using the response surface methodology. In Tables 4 and 5, the results of the regression analysis are presented for the Catuai Vermelho and Mundo Novo varieties.

Equations (1) and (2) represent the models selected according to the regression analyses for the varieties Catuai Vermelho and Mundo Novo, respectively. It can be observed in Tables 4 and 5 that the lack of adjustment for these models was insignificant.

[E.sub.d] = 39.422 - 3.031 * F - 15.260 * A + 1.126 * F * A ([R.sup.2] = 0.71) (1)

[E.sub.d] = 57.535 - 4.673 * F - 19.668 * A + 1.524 * F * A ([R.sup.2] = 0.80) (2)

where,

[E.sub.d]--cherry coffee fruit detachment efficiency, %;

A--amplitude, mm, and

F--frequency, Hz.

The selected models relate the cherry coffee fruit detachment efficiency to the vibration amplitude and frequency. These factors are associated to the acceleration reached by the system submitted to sinusoidal oscillation. In this type of motion, the RMS acceleration is proportional to the product of the amplitude and square of the vibration frequency.

In Figures 4 and 5 the surface responses are presented relating the cherry coffee fruit detachment efficiency to the vibration frequency and amplitude for the varieties Catuai Vermelho and Mundo Novo, respectively. It can be observed that for both varieties, the greatest detachment efficiency tended to occur at higher frequency and amplitude levels. Ciro (2001) obtained similar results analyzing coffee fruit detachment using a unidirectional slider crank shaker. Polat et al. (2007) also reported similar results when studying the mechanical harvesting of pistachio nuts. It was concluded that fruit removal percentage increased with an increase in shaking frequency and an increase in amplitude.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

In Figures 6 and 7, the response surfaces for cherry coffee fruit detachment efficiency are presented for different levels of vibration amplitude and frequency for both varieties. At the selected vibration amplitude levels, the effect of the vibration frequency on the detachment efficiency is shown.

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

It can be verified in Figures 5 and 6 that the cherry coffee fruit detachment efficiency tended to increase with higher values of frequency and amplitude for both studied varieties. This effect can be confirmed in the Tables 6 and 7, where the obtained experimental results of detachment efficiency are presented for different vibration frequency and amplitude values.

For both varieties, the frequency and amplitude combination of 26.67 Hz and 7.50 mm presented the highest fruit detachment efficiency. At this condition, average efficiencies were 65.25 and 84.65%, for the Catuai Vermelho and Mundo Novo varieties, respectively. Such results can be attributed to the increase of energy used in the fruit detachment process when the levels of these factors are increased (CIRO, 2001; POLAT et al., 2007).

The cherry coffee fruit detachment efficiency in the performed tests tended to be higher for branches of the Mundo Novo variety. This result can be attributed to the fact that the coffee fruit on the Mundo Novo variety branches were not bunched as close to each other as for the Catuai Vermelho variety. When the fruits are very close to each other, the motion of fruits during the vibration process is reduced complicating the fruits detachment.

Conclusion

Cherry coffee fruit detachment efficiency by vibration is directly related to vibration frequency and amplitude.

For both varieties studied, the cherry coffee fruit detachment efficiency tended to increase with the augment in vibration frequency and amplitude of the branches.

The vibration frequency of 26.67 Hz and amplitude of 6.25 mm tended to present higher cherry coffee fruit detachment efficiency for both varieties under study.

The cherry coffee fruit detachment efficiency by vibration for the Mundo Novo variety tended to be greater than that of the Catuai Vermelho variety for the frequency and amplitude intervals evaluated.

DOI: 10.4025/actasciagron.v32i3.6782

Acknowledgements

The authors thank the Foundation for Research Financial Support of Minas Gerais State, Brazil (FAPEMIG) and the Brazilian Consortium of Coffee Research and Development for their financial support granted for the accomplishment of this research.

Received on March 29, 2009.

Accepted on August 2, 2009.

References

CASTRO-GARCIA, S.; BLANCO-ROLDAN, G. L.; GIL-RIBES, J. A.; AGUERA-VEGA, J. Dynamic analysis of olive trees in intensive orchards under forced vibration. Trees, v. 22, n. 6, p. 795-802, 2008.

CIRO, H. J. Coffee harvesting I: Determination of the natural frequencies of the fruit stem system in coffee tress. Applied Engineering in Agriculture, v. 17, n. 4, p. 475-479, 2001.

PIMENTA, C. J.; VILELA, E. R. Efeito do tipo e epoca de colheita na qualidade do cafe. Acta Scientiarum. Agronomy, v. 25, n. 1, p. 131-136, 2003.

POLAT, R.; GEZER, I.; GUNER, M.; DURSUN, E.; ERDOGAN, D.; BILIM, H. C. Mechanical harvesting of pistachio nuts. Journal of Food Engineering, v. 79, n. 4, p. 1131-1135, 2007.

PRIETO, M.; MOUWEN, J. M.; PUENTE, S. L.; SANCHEZ, A. C. Concepto de calidad en la industria agroalimentaria. Interciencia, v. 33, n. 4, p. 258-264, 2008.

ROSA, U. A.; CHEETANCHERI, K. G.; GLIEVER, C. G.; LEE, S. H.; THOMPSON, J.; SLAUGHTER, D. C. An electro-mechanical limb shaker for fruit thinning. Computer and Electronics in Agriculture, v. 61, n. 2, p. 213-221. 2008.

SESSIZ, A.; OZCAN, M. T. Olive removal with pneumatic branch shaker and abscission chemical. Journal of Food Engineering, v. 76, n. 2, p. 148-153, 2006.

SOUZA, C. M. A.; QUEIROZ, D. M.; PINTO, F. A. C.; CORREA, P. C. Derrica de frutos de cafe por vibracao. Revista Brasileira de Armazenamento, Especial Cafe, v. 27, n. 4, p. 32-37, 2002.

SRIVASTAVA, A. K.; GOERING, C. E.; ROHRBACH, R. P. Engineering principles of agricultural machines. Michigan: ASAE, 1996.

TASCON, C. E. O.; MORA, R. B.; MEJIA, F. A.; ARISTIZABAL-TORRES, I. D.; GOMEZ, C. A. R.; URIBE, J. R. S. Cosecha del cafe con vibradores portatiles del tallo. Revista Facultad Nacional de Agronomia, v. 58, n. 1, p. 2697-2708, 2005.

WHITNEY, J. D.; BENSALEM, E.; SALYANI, M. The effect of trunk shaker patterns on florida orange removal. Applied Engineering in Agriculture, v. 17, n. 4, p. 461-464, 2001.

License information: This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Fabio Lucio Santos (1) *, Daniel Marcal de Queiroz (2), Francisco de Assis de Carvalho Pinto (2) and Nerilson Terra Santos (3)

(1) Departamento de Engenharia Mecanica, Universidade Estadual de Maringa, Av. Colombo, 5790, 87020-900, Maringa, Parana, Brazil. (2) Departamento de Engenharia Agricola, Centro de Ciencias Agrarias, Universidade Federal de Vicosa, Vicosa, Minas Gerais, Brazil. 3Departamento de Informatica, Centro de Ciencias Exatas e Tecnologicas, Universidade Federal de Vicosa, Vicosa, Minas Gerais, Brazil. * Author for correspondence. E-mail: flsantos@uem.br
Table 1. Levels tested for determining the coffee fruit
detachment efficiency.

Frequency (Hz)                  13.33, 16.67, 20.00, 23.33, 26.67
Amplitude (mm)                  3.75, 5.00, 6.25, 7.50
Direction of vibration          Longitudinal, transversal
Length of coffee branch (cm)    5, 10, 15

Table 2. Analysis of variance for cherry coffee fruit detachment
efficiency for the Catuai Vetmeiho variety.

SV                  DF       SS          MS          F       P-value

Frequency (F)        4    89937.16    22484.29      --         --
Branch length (C)    2     300.36      150.18    0.38 (ns)   0.6842
Direction of         1
vibration (D)        1     421.85      421.85    1.07 (ns)   0.3024
Amplitude (A)        3    37255.37    12418.46      --         --
F x C                8     4110.58     513.82    1.30 (ns)   0.2433
F x D                4     2093.37     523.34    1.32 (ns)   0.2611
F x A               12    23603.75    1966.98     4.98 *     <0.001
C x D                2     2079.72    1039.86    2.63 (ns)   0.0738
C x A                6     4274.05     712.34    1.80 (ns)   0.0987
D x A                3     856.52      285.51    0.72 (ns)   0.5393
F x C x A           24    13237.44     551.56    1.40 (ns)   0.1074
F x C x D            8     5745.84     718.23    1.82 (ns)   0.0738
F x D x A           12     5899.22     491.60    1.24 (ns)   0.2526
Residue             270   106684.91    395.13
Total               359   296500.16

* significant at 5% probability; (ns)non-significant.

Table 3. Analysis of variance for cherry coffee fruit detachment
efficiency for the Mundo Novo variety.

SV                  DF       SS          MS          F       P-value

Frequency (F)        4    123862.26   30965.57      --         --
Branch length (C)    2     5549.58    2774.79       --         --
Direction of
vibration (D)        1     1505.94    1505.94       --         --
Amplitude (A)        3    83065.35    27688.45      --         --
F x C                8     8308.73    1038.59     3.27 *     0.0014
F x D                4     2174.69     543.67    1.71 (ns)   0.1476
F x A               12    43719.43    3643.29     11.47 *    <0.001
C x D                2     3023.46    1511.73     4.76 *     0.0093
C x A                6     2246.64     374.44    1.18 (ns)   0.3177
D x A                3     366.76      122.25    0.38 (ns)   0.7639
F x C x A           24    10757.18     448.22    1.41 (ns)   0.1002
F x C x D            8     2661.94     332.74    1.05 (ns)   0.4004
F x D x A           12     4511.16     375.93    1.18 (ns)   0.2945
Residue             270   85746.38     317.58
Total               359   377499.49

* significant at 5% probability; (ns) non-significant.

Table 4. Regression analysis for the cherry coffee fruit
detachment efficiency for the Catuai Vermelho variety considering
the frequency and amplitude of vibration factors.

SV                                  DF        MS

Regression                          3     47894.16 *
Lack of adjustment                  16    503.78 (ns)
Frequency, Amplitude, Frequency x
Amplitude                           19      1698.49
Residue                             270     395.13
Total                               359

* significant at 5% of probability. (ns) non-significant.

Table 5. Regression analysis for the cherry coffee fruit
detachment efficiency for the Mundo Novo variety considering the
frequency and amplitude of vibration factors.

SV                                  DF        MS

Regression                          3     80285.34 *
Lack of adjustment                  16    533.69 (ns)
Frequency, Amplitude, Frequency x
Amplitude                           19     2544.24
Residue                             270     317.58
Total                               359

* significant at 5% of probability; (ns) non-significant.

Table 6. Experimental results of the cherry coffee fruit
detachment efficiency (%) obtained for the Catuai Vermelho
variety as a function of vibration amplitude and frequency.

Frequency (Hz)        Amplitude (mm)

                 3.75    5.00    6.25    7.50

13.33            3.11    0.62    0.79    0.27
16.67            1.25    4.48    5.81    10.95
20.00            1.58    11.66   18.86   38.46
23.33            4.78    26.34   32.18   50.35
26.67            14.66   40.42   58.76   65.25

Table 7. Experimental results of the cherry coffee fruit
detachment efficiency (%) obtained for the Mundo Novo variety as
a function of vibration amplitude and frequency.

                      Amplitude (mm)

Frequency (Hz)   3.75    5.00    6.25    7.50

13.33            0.00    0.00    5.77    2.40
16.67            5.54    2.79    11.42   13.75
20.00            1.02    10.12   24.60   58.00
23.33            6.17    26.51   44.81   71.99
26.67            17.60   37.31   67.00   84.65
COPYRIGHT 2010 Universidade Estadual de Maringa
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2010 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:texto en ingles
Author:Santos, Fabio Lucio; Marcal de Queiroz, Daniel; de Carvalho Pinto, Francisco de Assis; Terra Santos,
Publication:Acta Scientiarum Agronomy (UEM)
Date:Jul 1, 2010
Words:3030
Previous Article:Meiotic behavior in Panicum maximum Jacq. (Poaceae: Panicoideae: Paniceae): hybrids and their genitors.
Next Article:Adaptability and stability of semilate and late maturing soybean genotypes in Minas Gerais state.
Topics:

Terms of use | Copyright © 2017 Farlex, Inc. | Feedback | For webmasters