## 5 Conclusions  
The research results presented in this paper show that the loads and power losses due to friction in the joints of the loader manipulator mechanisms depend on the transformation and transmission parameters of the mechanisms. The transformation parameters refer to the diameters of the pistons and piston rods of the hydraulic cylinders, while the transmission parameters represent the coordinates of the connections between the hydraulic cylinders and the linkage levers for individual members of the manipulator's kinematic chain. All generated variant solutions satisfy the required functional constraints: declared digging force, geometry limits, and avoidance of dead points. Using MSC Adams, the operation of the developed loader model was simulated with different variants of the Z-kinematic manipulator drive mechanisms. The simulation was performed under identical parameters for the manipulation task operations: loading, material transfer, and unloading. During the loading operation, the material resistances were modeled using the resistance force and resistance moment vectors and determined using the discrete element method (DEM). \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Manipulator Variant**} & \multicolumn{3}{c}{**Piston/Piston Rod Diameter**} & \multicolumn{2}{c}{**Objective Function**} & \multicolumn{1}{c}{**Criterion Indicator**} \\ \cline{2-7}  & \(D_{3}\) & \(d_{3}\) & \(D_{4}\) & \(d_{4}\) & \\ \cline{2-7}  & [mm] & [mm] & [mm] & [mm] & \(f_{t}\) & \(p_{t}=f_{t\,min}/f_{t}\) \\ \hline V.001 & 125 & 90 & 150 & 100 & 425.137 & 0.875 \\ V.014 & 125 & 80 & 160 & 100 & 541.580 & 0.687 \\ V.020 & 125 & 80 & 140 & 90 & 446.604 & 0.833 \\ V.026 & 110 & 80 & 170 & 115 & 473.667 & 0.785 \\ V.028 & 110 & 80 & 180 & 115 & 513.465 & 0.725 \\ \hline V.033 & 140 & 90 & 160 & 110 & 634.874 & 0.586 \\ V.036 & 125 & 90 & 150 & 100 & 424.215 & 0.877 \\ V.051 & 150 & 100 & 170 & 110 & 708.934 & 0.552 \\ V.053 & 125 & 90 & 150 & 100 & 498.660 & 0.746 \\ V.064 & 140 & 90 & 150 & 100 & 598.755 & 0.621 \\ \hline V.095 & 125 & 90 & 140 & 100 & 448.396 & 0.830 \\ V.108 & 150 & 100 & 180 & 125 & 674.644 & 0.532 \\ V.111 & 110 & 80 & 170 & 115 & 470.975 & 0.790 \\ V.117 & 140 & 90 & 125 & 090 & 476.138 & 0.781 \\ V.135 & 125 & 90 & 150 & 100 & 425.254 & 0.875 \\ \hline V.147 & 140 & 90 & 160 & 100 & 641.743 & 0.580 \\ V.150 & 125 & 90 & 160 & 100 & 515.947 & 0.721 \\ V.178 & 150 & 100 & 150 & 100 & 602.219 & 0.618 \\ V.223 & 125 & 80 & 150 & 100 & 509.715 & 0.730 \\ V.236 & 110 & 80 & 170 & 110 & 476.795 & 0.780 \\ \hline V.245 & 150 & 100 & 140 & 90 & 615.591 & 0.604 \\ V.267 & 125 & 80 & 170 & 115 & 559.207 & 0.665 \\ V.271 & 110 & 80 & 140 & 100 & \(f_{t\,min}=372.014\) & \(p_{t\,max}=1.000\) \\ V.278 & 110 & 80 & 160 & 100 & 444.064 & 0.838 \\ V.290 & 125 & 90 & 160 & 100 & 524.807 & 0.709 \\ V.295 & 125 & 90 & 150 & 100 & 516.179 & 0.721 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Objective functions and indicators of the tribological criterion of manipulator mechanisms. The analysis results show that the variants of the loader manipulator mechanisms with smaller transformation parameters, compared to those with larger ones, have lower power losses caused by friction between the elements of the kinematic pairs. This is because, under the same manipulation task conditions, the forces in the joints of the mechanisms are smaller. Due to the reduced forces, the dimensions (diameters) of the joint bolts are smaller, and therefore the moments and friction forces between the joint elements are also smaller. While larger hydraulic cylinders are typically used to achieve higher digging forces, smaller hydraulic cylinders offer benefits such as reduced size and potential cost savings. However, their use involves several important trade-offs that must be carefully considered. These include increased leakage risks due to higher operating pressures, greater heat generation, reduced durability of seals and components, and a potentially slower dynamic response.