development and testing of a portable palm tree pruning machine

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variables. The regression model is indicated in equation 2. As shown, the cutting power required
for fresh petioles (60-75% MC) is 12 W/cm 2 while it is 27 W/cm 2 at more dry petioles (about
17% MC).
P = 32.17 − 0.3145 MC, R
2 = 0.86
(2)
where: MC= petiole moisture content, %
P= power required to cut 1 cm 2 of petiole cross section area (W).
Fig. 5 shows that the required time of petiole cutting is proportional to the petiole MC.
The R 2 of this relationship was found to be 0.81 suggesting a linear relationship. The regression
model is indicated in equation 3. As shown in Fig. 5, the fresh cut petioles of 60 to 75% MC
required a cutting time of at least 3 sec/cm 2 while the dried cut petioles of 5 to 15% MC required
about 0.9 sec/cm 2 . Clearly, the fresh cut petioles required more time than the dried ones. This is
attributed to the fact that moisture makes petiole fibers stronger and more tied to each other.
Thus, the petiole becomes more resistant to cutting.
T = 0.4187 + 0.0432 MC, R
2 = 0.81
(3)
where: T= time required for cutting (sec/cm 2 ),
MC= petiole moisture content, %.
Figure 6 shows that the energy required for cutting is proportional to the petiole MC.
Obviously, increasing petiole moisture content increased the cutting energy due to increasing
cutting time. Again, the fresh petioles of 60 to 75% MC required a cutting energy of 30 to 35
W.sec/cm 2 , while the dried petioles of 5 to 15% MC required 12 to 15 W.sec/cm 2 . The R 2 value
of the relationship was 0.71 suggesting a linear relationship. The regression model is indicated in
equation 4.
E = 7.13 + 0.399 MC, R
2 = 0.71
(4)
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