Design and experiment of multi-link profiling Citrus reticulata ‘Chachi’ peeling mechanism

Citrus reticulata ‘Chachi’ cultivated in Xinhui, Guangdong, is the sole source of "Southern Medicine" pericarp of dried tangerine. This processed product has been known as the pericarp of Citrus reticulata ‘Chachi’. There are functions of drying dampness, resolving phlegm, regulating Qi, and invigorating the spleen, particularly for its excellent health benefits in cardiovascular, respiratory, endocrine, gastrointestinal, and cosmetic aspects, according to the concept of medicinal food homology. These characteristics have endowed the Citrus reticulata ‘Chachi’ with high medicinal and economic value, thus resulting in the ever-increasing production and output value in recent years. However, the traditional processing of Citrus reticulata ‘Chachi’ in peeling and flesh extraction has suffered from low automation and the juice splashing onto the peel for corrosion failure (commonly known as "burning the peel"). In this study, an automatic device of peeling and flesh extraction was developed for the Citrus reticulata ‘Chachi’, according to the profiling mechanism. Initially, advanced 3D scanning and reconstruction were employed to acquire the real motion trajectory and posture data of fruit peel during manual peeling. Due to the three-fold symmetry, only one-third of the peel was scanned during manual peeling. Six key positions and postures were then selected to establish the curve model of profiling target posture. The coupling relationship between the position and posture of fruit peel during Citrus reticulata ‘Chachi’ peeling was deduced, according to the posture curve and fitting equation. A mathematical model was then established for the posture of manual peeling in the accurate design of subsequent devices. Subsequently, the conceptual design was combined with the mechanical design to devise a set of multi-link profiling mechanisms. According to the postures of various linkages, a cross-type double rocker mechanism was determined as the prototype of the multi-link profiling mechanism. A mechanism approximating the target posture (manual peeling posture) was designed using dimensional synthesis. A rocker-slider and a cross-type double rocker mechanism in series were coordinated with the vacuum sucker adsorption. The motion trajectory of manual peeling was simulated to closely approximate the position and posture during real peeling. The efficiency and accuracy of the device were verified after precise design and optimization. Subsequently, simulation analysis was conducted to validate the performance of the multi-link profiling mechanism. The simulation has verified the stability and reliability of the device during peeling. Furthermore, a physical device was manufactured to conduct the actual peeling experiments. The experimental results demonstrate that the device accurately performed the mimic manual peeling postures, thus achieving mechanical peeling of Citrus reticulata ‘Chachi’. Additionally, an enveloping flexible mechanical claw was designed for the damage-free peeling and flesh extraction of Citrus reticulata ‘Chachi after peeling operation with the multi-link profiling device’. The peel of Citrus reticulata ‘Chachi’ was greatly protected to enhance the efficiency of flesh extraction. The test results show that the nondestructive rate of peeling was 80%. The peeling and flesh extraction were optimized to successfully improve the initial processing of Citrus reticulata ‘Chachi’. The non-destructive mechanical peeling and flesh extraction of Citrus reticulata ‘Chachi’ were integrated into the industrial production lines, thus significantly improving production efficiency and cost savings. Therefore, the findings can provide valuable references for similar fruit processing. The profiling mechanism was integrated with the processing techniques. The non-destructive peeling and flesh extraction were achieved for the modernization and intelligence of agricultural product processing. Thus, practical technical support and valuable experience were offered for the Citrus reticulata ‘Chachi’ industry.