Stability Analysis of Self Propelled Multi-Utility Platform for Orchard Management 1 System using Point Manipulation Method

6 Self-propelled hydraulically operated multi-utility platform for orchard management system 7 (SOMS) was developed to increase the accessibility of pickers to fruit on trees and to carry 8 out orchard management practices like spraying and pruning. The platform was designed for 9 vertical reach of 6 m and load carrying capacity of 200 kg. Point manipulation programme 10 was developed by Microsoft Excel add in and by trial and error, position of the standard 11 components were decided to determine the centre of gravity of the machine. Standard 12 components were placed over the chassis in such an arrangement that, the centre of gravity 13 (CG) always remain over the chassis during entire operation of the platform from minimum 14 to maximum height with designed load. Forces acting on the chassis were analyzed to find 15 out weight transfer and impending stability in various terrain conditions, various bucket 16 positions loads on the bucket. The prediction equation for the determination of horizontal 17 center of gravity (X cg ) was verified with the true value collected by keeping the wheels of 18 SOMS on individual electronics weighing balance. The average absolute variations between 19 the predicted and measured values of X cg were within 0.44 % and 3.53%. 20


Introduction 23
Fruit crops like mango, cashew, coconut, litchi and arecanut etc. are cultivated on large area 24 in India. Harvesting, pruning and spraying of these horticultural fruit trees are difficult due to 25 height of trees and non availability of machines. It requires fairly large numbers of seasonal 26 labour. It is difficult to pick fruits from tall trees and usually costs more for harvesting, 27 pruning and spraying operations. Manually operated low capacity gadgets and tree-shaking more stable in undulated terrain, but manoeuvrability inside the orchard is a difficult task. As 35 orchard holdings are small in size in India, their adaptability is less because of large turning 36 radius. Many cases canopy structure of the plant doesn't permit to move the machine easily.

37
In many surveys, it was reported that the catching and collecting system was effective with 38 low damage inflicted to fruits. These harvesters allow user to reach 6 to 10 m, but turnover 39 accidents is a major concern. French Mutualité Sociale Agricole, the second largest social  where,  is the coefficient of friction between the wheel and ground surface and N is the 82 normal reaction. Considering value of  as 0.85 and 70% of the total SOMS weight 83 distributed over the rear traction wheel, F s was calculated as 7.5 kN.

84
The wheel torque (T) is assumed equal to the total force required F t acting at a moment arm 85 equal to the rolling radius (r). Torque requirement was calculated for four conditions such as:

86
(i) SOMS operating on level terrain (ii) SOMS moving up the gradient (iii) SOMS 87 descending in gradient and (iv) SOMS starting on gradient. SOMS operating on level terrain, 88 only rolling resistance was considered where as for the SOMS moving up the gradient, both 89 rolling resistance and gradient force was considered. SOMS descending on the gradient, 90 gradient will add the drive. SOMS starting on the gradient, maximum torque which can be 91 applied at the wheel is that which will cause the wheel to slip.

92
Torque requirement when SOMS moving on level terrain is given by the expression,

94
Torque requirement when SOMS moving up the gradient is given by the expression, Torque requirement when SOMS descending on the gradient is given by the expression, Torque requirement when SOMS starting on the gradient is given by the expression, Torque required for the SOMS at individual drive wheel for conditions (i), (ii), (iii) and (iv)

102
Based on the maximum torque requirement, hydraulic system was designed and the circuit 103 was developed (Fig.1). The open loop hydraulic system was adopted to power the vehicle as 104 well as lifting and lowering the arm. Since machine was conceptualized with three wheel 105 systems, the two wheels are required to be powered and third wheel should be caster wheel 106 for self-steering. Hydraulic system was designed for forward and reveres movement, steering, Where, d is the diameter of rod in cm.

159
The lift arm is key component which carries the entire load. It is an overhanging cantilever The horizontal center of gravity of SOMS was calculated by using the following expression:

192
Weight distribution and position of centre of gravity found from the above analysis at zero 193 fruit load condition standing on the level ground is summarized in Table 2.

194
The concept was translated in solid model using CAD software PTC Creo element 1 (Fig. 4)

195
Aanalysis were per-formed based on maximum weight of various components as well as  Table 3.

Stability analyses 200
As the vehicle is designed for the field application, it has to ride over very rough terrain.

201
Safety of the operator should be the primary issue, while designing this type platform.

202
Stability calculation must be done before being used for the field application. The complete 203 process includes the proper selection of shape and dimensions, weight distribution etc.

204
Position of centre of gravity plays an important role in deciding the stability of the platform.

213
The vehicle is supported by the ground, with its three wheels, and creates a triangle. As long 214 as the line of center of gravity remains in the area of the triangle, the machine will be stable.

Static and dynamic analysis of the lateral stability 243
Lateral stability of the SOMS in static and dynamic condition was analysed for the slope of the distance between wheel centres, the X cg was calculated.

296
The comparison of measured and predicted values of the X cg w.r.t to the height of the bucket 297 of SOMS for all terrain conditions and two extreme loading conditions (no load and 298 maximum design load) are plotted in Fig. 9. A close relationship was found between the 299 measured and predicted value of X cg . For lateral slope, the developed equation under 300 predicted whereas for all other three terrain conditions it was over predicted. The measured 301 and predicted values of the X cg for all terrain conditions are plotted in Fig. 10 and results of 302 statistical analysis for model validation are given in  with the aim to decrease the hazards associated with field application. This not only helps the 321 operator for safe operation but also future industry for development of these types of elevator 322 lift.