# Design and Control Simulation Analysis of Tender Tea Bud Picking Manipulator
## 5 Experiments and Results
In Figure 17, for the lifting angle control, SMC-PID demonstrates greater accuracy compared to traditional SMC and PID control. The overshooting amount for PID control is 11.6%, whereas SMC-PID exhibits no obvious overshooting with the shortest adjustment time being 1.28 s. This indicates that SMC-PID achieves more precise control with minimal overshooting during the lifting and pulling operation. In Figures 18 and 19, upon comparing the angular velocity curves of the three control algorithms, it is evident that the peak value of the angular velocity is the smallest in SMC-PID, and the angular velocity curve returns to a smooth state more quickly. Therefore, SMC-PID control exhibits superior motion smoothness, indicating that the robot can reduce swing and jitter during the motion process, making the robot's movement smoother and more stable. This observation emphasizes that SMC-PID control is softer, more accurate, and more reliable, with no overshoot. It proves to be better suited for satisfying the demand of picking tender tea buds compared to traditional SMC and PID control methods. In the picking process, to ensure the smooth picking of tender tea buds, it is essential to measure the lifting distance of the picking robot. As shown in Figures 20 and 21, the X-axis lifting distance is approximately 37.7 mm, and the Y-axis lifting distance is about 107.5 mm. Additionally, Figure 22 illustrates that the combined displacement of the manipulator is  
Figure 19: Comparison of angular velocity control of a picking manipulator lifting at 45\({}^{\circ}\). \begin{table}
\begin{tabular}{c} **Lift Overshoot** \\ **(\%)** \\ \end{tabular} \\ \hline
1 & PID & 0.76 & 1.42 & 3.37 & 11.6 \\
2 & SMC & \(\backslash\) & \(\backslash\) & \(\backslash\) & \(\backslash\) \\
3 & SMC-PID & 0.715 & 1.28 & 1.38 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Controller adjusts time and overshoot comparison table. Figure 18: Comparison of angular velocity control for a 30\({}^{\circ}\) rotation of a picking manipulator. A manipulator model was established in SolidWorks 2021, and its mechanical structure was verified through finite element analysis. Additionally, a PVDF piezoelectric thin film sensor was introduced and mounted on the mechanical finger for simulation experiments. The results of the experiments confirmed the rationality of the mechanical structure, and the introduction of the PVDF piezoelectric thin film sensor successfully validated the manipulator's ability to meet design requirements. It demonstrated the capability to effectively reach into the complex growth environment of tea leaves for picking. (2) Joint simulation is conducted in MATLAB/Simulink 2021 and Adams 2020 software. The SMC-PID controller is designed in Simulink, enabling the control of the closed-loop system's angular and angular velocity error feedback by adjusting PID parameters. This adjustment facilitates the quick convergence of sliding mode control to the sliding mode surface. The regulation time and overshoot are significantly reduced in comparison with traditional PID and SMC control methods. In the control of the clamping force, the composite control method effectively mitigates the jump phenomenon of the clamping force during the picking process. Simulation results demonstrate that the SMC-PID controller exhibits higher control accuracy, stability, and response speed when compared to traditional PID and SMC control methods. Methodology, P.X. and Q.L. ; Validation, P.X. ; Resources, Q.L. ; Data curation, G.F.; Writing--original draft, P.X. ; Writing--review & editing, G.F.; Project administration, Q.L. and G.F. All authors have read and agreed to the published version of the manuscript. This research was funded by The National Key Research and Development Program of China grant number 2022 YFF0607403 and was funded by Supported by The National Natural Science Foundation of China grant number 61971048. Not applicable. Data Availability Statement: Data are contained within the article. The authors declare no conflicts of interest.