To improve the performance of piezoelectric (PZT) jetting dispensers in the electronic packaging industry and address the problems of oversized, easily fatigued elastic hinges and low repetition accuracy of conventional PZT jetting dispensers with a compliant mechanism-based lever, a new double needle PZT jetting dispenser prototype was developed. The advantage of the proposed structure over compliant mechanism-based lever was demonstrated by dynamics analysis. Firstly, the design stroke of the needle and the modal state of the dispenser body were analyzed using ANSYS. Secondly, the theoretical model of adhesive injection was established, the fluid pressure change process inside the nozzle during the working cycle of the jetting dispenser was simulated using Fluent, and the effects of the supply pressure and needle stroke on the injection speed of the droplet were investigated. Finally, a test bench was built to conduct the experiment, and the results showed that the supply pressure and the driving signal duty cycle between 20% and 80% were positively correlated with the size of droplet diameter, whereas the driving signal frequency was negatively correlated with the droplet diameter, thereby validating the proposed adhesive injection model. Under the experimental conditions, the highest operating frequency of the designed PZT jetting dispenser was 400 Hz, which is close to the high-frequency level of existing studies, and the minimum droplet diameter obtained was 0.36 mm, which is 0.1–0.2 mm less than that of the existing PZT jetting dispenser with a compliant mechanism drive, meeting the industry requirements for the working performance of a PZT jetting dispenser.

The recognition of fresh tea leaf sprouts is one of the difficulties in the realization of the automated picking of fresh tea leaves. At present, the research on the detection of fresh tea leaf sprouts is based on a single variety of tea leaves for a specific period or specific place, which has no advantage for the spread, promotion, and application of the methods. To address this problem, an identification of multiple varieties of tea sprouts (IMVTS) model was proposed. First, images of three different varieties of tea (ZhongCha108 (ZC108), ZhongHuangYiHao (ZH), ZiJuan (ZJ)) were obtained, and the multiple varieties of tea (MVT) dataset for training and validating models was created. In addition, the detection effects of adding a convolutional block attention module (CBAM) or efficient channel attention (ECA) module to YOLO v7 were compared. In the detection of the MVT dataset, YOLO v7+ECA and YOLO v7+CBAM showed a higher mean average precision (mAP) than YOLO v7, with 98.82% and 98.80%, respectively. Notably, the IMVTS model had the highest AP for ZC108, ZH, and ZJ compared with the two other models, with 99.87%, 96.97%, and 99.64%, respectively. Therefore, the IMVTS model was proposed on the basic framework of the ECA and YOLO v7. To further illustrate the superiority of the model, this study also conducted a comparison test between the IMVTS model and the mainstream target detection models (YOLO v3, YOLO v5, FASTER-RCNN, and SSD) and the IMVTS model on the VOC dataset, and it is clear from the test results that the mAP of the IMVTS model is ahead of the remaining models. Concisely, the detection accuracy of the IMVTS model can meet the engineering requirements for the automatic harvesting of autumn fresh famous tea leaves, which provides a basis for the future design of detection networks for other varieties of autumn tea sprouts.

Agricultural and Biological Engineering

Piezo-driven dispensers are precision dispensing devices for trace amounts of fluid and are widely used in the microelectronics packaging field. However, the preloading mechanism of piezo-driven dispensers easily loosens in high-frequency operation, and the design accuracy of the transmission ratio of the flexible displacement transmission mechanism (DTM) requires improvement. To address the aforementioned problems, we designed a self-locking preloading mechanism with an adjustable preloading amount for piezo-driven flexible transmission dispensers and investigated the method of designing the transmission ratio considering the non-expected directional deformation (parasitic deformation). First, the principle of the preloading mechanism was analyzed, and a method for adjusting the droplet diameter based on the preloading amount was proposed. Second, an asymmetric flexible-hinge compliance matrix calculation method was proposed, a transmission ratio model of the DTM was established, and the influence law of the structural parameters on the transmission ratio was comparatively analyzed using ANSYS software. Based on the output displacement requirement, transmission ratios were designed and structural parameters were determined. Finally, based on the piezoelectric coupling simulation, a piezo-driven dispenser was manufactured, and a test platform was built to conduct the relevant tests. The simulation and test results demonstrated that the maximum relative errors of the transmission-ratio calculated by the proposed transmission-ratio model were 1.54% and 3.6%, respectively, compared to the simulation and test results, confirming that the model was correct. Single-factor tests confirmed that a preloading mechanism can fix and preload the piezostack and that the droplet diameters can be adjusted with the preloading amounts. The operating frequency was up to 800 Hz with a diameter of 0.30 mm and a consistency of 4.32%, which meet the requirements of dispensing efficiency in the microelectronics packaging field. This study has practical significance for enhancing the transmission ratio design accuracy and dispensing performance of dispensers.

The elevation detection accuracy of the laser receiver in the laser levelling control system directly affects land-levelling operations. To effectively improve the effect of levelling operations and meet the requirements for the accuracy of elevation detection in different industries, this study optimization designed a multilevel adjustable laser receiver. First, we examined the laser signal detection technology and processing circuit, designed the photoelectric conversion array for the detection of the rotating laser, and converted it into a photocurrent signal. We also designed the filter, amplifier, and shaping and stretching circuits for analogue-to-digital conversion of the photocurrent signal. The digital signal was calculated based on the deviation of the elevation by using a microprocessor and was output by a controller area network (CAN) bus. The laser beam spot diameter transmission and diffusion were then studied, and with the detectable spot diameters were compared and analyzed. Accordingly, an algorithm was proposed to calculate the deviation of laser receiver elevation. The resolution of the elevation deviation was set to ±3 mm; however, this value could be adjusted to ±6 mm, ±9 mm, ±12 mm, and ±15 mm, according to the requirements. Finally, the laser receiver was tested and analyzed, and the test results of the elevation detection accuracy showed that when the laser receiver was within a radius of 90 m, the elevation detection accuracy was within the ±3 mm range. The outcomes of the farmland-levelling test showed that the standard deviation $S_d$ of the field surface decreased from 9.54 cm before levelling to 2.42 cm after levelling, and the percentage of sampling points associated with absolute errors of ≤3 cm was 84.06%. These outcomes meet the requirements of high-standard farmland construction. The test results of concrete levelling showed that within a radius of 30 m, the standard deviation $S_d$ of the elevation adjustment of the left laser receiver was 1.389 mm, and the standard deviation $S_d$ of the elevation adjustment of the right laser receiver was 1.316 mm. Furthermore, the percentage of the sampling points associated with absolute elevation adjustment errors of ≤3 mm in the cases of the two laser receivers was 100% after levelling, whereas the standard deviation $S_d$ of the sand bed surface was 0.881 mm. Additionally, the percentage of the sampling points associated with absolute errors of ≤3 mm was 100%. This met the construction standards of the concrete industry.