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Trunk shakers perform a forced vibration that should be set according to tree species and architecture to efficiently detach fruits. However, manufacturing companies produce designs that are poorly customisable according to different trees. This work presents a prototype that is configurable in amplitude and frequency of vibration, which has been developed to generate the different vibration patterns required by various fruit trees. To study the feasibility of the developed technology, we built a test bench with a post, to which we fixed olive, almond and orange tree branches, and tested different configurations of the machine (frequencies from 12.25 to 20.75 Hz and eccentricities from 58 to 86 mm). Acceleration values were recorded at different points: the trunk shaker, the post in the grip, the top of the post, and in each branch. We recorded a large loss of acceleration transmissibility between the shaker and the post (20%–60%) due to existing frictions that dissipate energy through heat loss. There is a non-linear increase between vibration frequency and the resultant acceleration value recorded, as well as with increasing eccentricity. The shaker was able to provide a different vibration pattern in each configuration, affecting the transmission of vibration in each of the branches studied, for which mean acceleration transmissibility ranged between 82% (almond), 104% (olive) and 136% (orange). [ABSTRACT FROM AUTHOR]

Harvesting in intensive olive orchards is usually performed with trunk shakers. Many challenges remain both to the implementation of integral harvesting systems and to improving their detachment efficiency without a dependence on manual labour. This work develops a prototype over-the-row harvester that incorporates two harvesting systems which can work simultaneously: a trunk shaker and two canopy shakers. The objective is to characterise the dynamic effect of each system and determine the best configuration for efficiency and damage control regarding feasibility of use. The trunk shaker in isolation has a predominantly dynamic effect with very high acceleration values that slightly increased with the addition of the canopy shaker systems. In all cases, acceleration transmissibility between the trunk and branches amplified, and increased between 8% and 17% at low and high frequencies, respectively, when the trunk shaker worked in conjunction with the canopy shakers. The increase in resultant acceleration did not correlate with the increase in detachment percentage or with the amount of damage due to the impact generated by the canopy shaker. However, this effect is observed in the vibration pattern generated by both systems. Configuration of the trunk shaker at 21.4 Hz and the canopy shakers at 3.6 Hz reported detachment efficiencies higher than 85% and damage less than 3 kg per 100 kg of fruit. The results show a feasible alternative to the harvesting systems habitually employed in intensive olive orchards, which require tree training adapted to the type of machine in order to improve efficiency and reduce damage. [Display omitted] • A new over-the-row harvester with trunk and canopy shaker has been developed. • The shaker systems have a different vibration pattern that complements each other. • It is a valid solution to intensive olive harvesting due to its high efficiency. • The trunk shaker is the system with most influence on the tree dynamic behaviour. • A suitable combination is trunk shaker at 21.4 Hz and canopy shaker at 3.6 Hz. [ABSTRACT FROM AUTHOR]

The development of trunk shaker machines over the years has been based on test-error methods in field. Mathematical or computational models have been studied with great simplifications. This paper presents a method for modelling the dynamic behaviour of a trunk shaker with a test bench. Two mass configurations were used on the test bench as well as two different vibration frequencies on the trunk shaker. Acceleration values were recorded at different points of the system. The binomial shaker-post was computationally modelled, and its dynamic response was analysed based on a modal and transient study with a series of proposed simplifications. The results of the simulations were compared with experimentally recorded acceleration values. In both cases, a linear response to mass and frequency variation was observed in the acceleration that the shaker performed. There was a high correlation in the effective accelerations (error < 4%) between experimental and computational studies measured in the trunk shaker. However, there were higher errors when the post was used in the test in the post structure points. The greatest uncertainty in the model may lie in the assumption of contact between the attachment pad and the post, but if this is not carried out, it makes convergence in the computational calculations very difficult. The method has proved its worth in determining the dynamic behaviour of these machines. [ABSTRACT FROM AUTHOR]

• A simplified model for simulation of the dynamic behaviour of branches is proposed. • The main average mechanical parameters of the simulation process are determined. • A simple device for modelling branch geometry has been developed. • It is possible to predict the modal behaviour with high accuracy. • The effect of leaves modifies the dynamic response and must be included in models. The application of vibration in the mechanical harvesting of fruit trees is a determining factor to achieve fruit detachment. The acceleration required to do so is experimentally determined in expensive tests using different machines and configurations. A simple, appropriate model that could predict the vibration response of plant matter might facilitate these simulations of different conditions and optimise the process. Several mathematical and computational models exist that employ great simplifications and produce uncertain results. We propose a computational model for simulating the dynamic response of branches with and without foliage under forced vibration, applied to the case of the olive tree. We also present a method for characterising the mechanical properties necessary to conduct the simulation using commercial software, Ansys, and the experimental determination of the properties. To do so, we propose some simplifications in the modelling. Next, computational simulations replicate the same conditions as the real vibration tests conducted in the laboratory, and the accelerations produced at the origin and ends of the branches are determined. The results offer a good degree of similarity between the calculated and experimental values in terms of natural frequencies, although some dispersion of transmissibility exits between the origin and ends of the branches, above all for larger branches and when considering their foliage. Branches without leaves had lower natural frequencies. The damping coefficient of branches with leaves was almost twice than ones without although the acceleration transmissibility is much bigger. [ABSTRACT FROM AUTHOR]

The current commercial technologies for mass harvesting fruit are based on the application of forced vibration to the tree, which is transmitted to the fruits causing their detachment. The dynamic behaviour of the plant under forced vibration is of special interest to improve the design and use of the machinery. The objective of this work is to determine the effect of fruit and leaves on the dynamic response of the citrus branch. In this study, 22 secondary branches of 'Valencia' sweet orange trees were tested by applying forced vibration and measuring the response of the branches with triaxial accelerometers. The branches were tested in three stages: in-fruit branch, out-of-fruit branch and out-of-leaf branch. Three natural frequency values were identified in the branches, and were established as 2, 7 and 11 Hz. Acceleration transmissibility along the branch decreased as vibration frequency increased. The acceleration transmission values were highest for the first natural frequency, and were up to 1.3-fold greater in the out-of-fruit branch and up to 4.6-fold greater in the out-of-leaf branch. The presence of fruits on the branch did not modify the branch natural frequency values but did slightly reduce the values of acceleration transmissibility. However, the presence of leaves on the branches had a double effect, reducing the first natural frequency and drastically damping acceleration transmissibility. Image 1 • Tested citrus branches showed a similar frequency response to each other. • Three natural frequencies at 2, 7 and 11 Hz were identified in branch response. • Removal of fruit and leaves amplified vibration 1.3 and 4.6-fold, respectively. • Fruit did not modify the natural frequency values of the branch. • Leaves reduced the first natural frequency and drastically damped the vibration. [ABSTRACT FROM AUTHOR]

Trunk shakers are widely used for olive harvesting, being the main detachment system for fruit harvesting. In recent decades, the components of trunk shakers have evolved at mechanical, hydraulic and control levels. However, machine accuracy depends on the operator, whose expertise is a key factor for issues such as trunk debarking caused by grabbing systems, shaking parameters, or on-foot operator safety. The objective of this work was to develop an automatic trunk-detection system to reduce operator influence on the process. Thus, the automatic system via infrared sensor was implemented on a trunk shaker head hitched to a tractor. A control algorithm, control logic and display for trunk grabbing automation were developed. The automatic system was tested under laboratory and field conditions to assess the influence of some variables on trunk detection. The evaluated variables were colour, material, diameter, and target location within the sensor field of vision. The success rate of the automatic system was 91% for trunk grabbing. In the field phase, the efficacy of the automatic system was compared to an operator performing the tasks manually, obtaining times of 16.05 ± 2.8 s tree −1 and 21.54 ± 5.29 s tree −1 respectively, and a percentage of success in trunk grabbing of 92.9%. Automatic mode improved manual mode by saving 27.3% of time, improving effective field capacity. The automatic mode developed here provided a high ratio of success and it showed highly reliable and efficient performance compared with manual mode. [ABSTRACT FROM AUTHOR]