# C-Legged Hexapod Robot Design Guidelines Based on Energy Analysis
## 4 Design Parameters Impact on Power Demand and Energy Consumption
### Design Parameters Recommendations  
The relationship obtained between the parameters analyzed and the peak power demand and the distance covered with one joule are sum up in the Table 3, the meaning of the different colors and acronyms are shown below this table. Once again, it is worthwhile noting, that even though a simple C-leg system has been considered throughout the article, the conclusions obtained are the same as they would be for a full C-legged hexapod robot moving with all six legs synchronized. In an alternating tripod gait, the impact of the parameters investigated affects the energy and power consumption according to the synchronization of the two tripods, and can, therefore, be reduced. With the conclusions obtained in the analysis performed in this section, the following recommendations are suggested to produce an efficient and well dimensioned C-legged hexapod robot. The following recommendations are for generic hexapod robots with no energy recovery, and therefore, no numbers that might be different for particular cases are used:  
* **Energy-Efficiency:** To produce a robot efficient in the transformation of joules to distance covered, the mass has to be kept as low as possible. This is because the KE and GPE variations are increased, and that implies a greater loss of energy. For this reason, the mass reduction should be the main objective throughout the design stage. * **Motor Selection:** Special care has to be taken when selecting the motors; as motors with high revolutions will need to supply really high-power demands. With the results obtained in Section 4, it is not recommended to have angular speeds over 140 rpms when the leg is in contact with the grounds, as higher rpms will lead to massive peak power demand, requiring the motor to be very powerful and to have high torque. Selecting a motor with so much power might also have the drawback of increased mass, which ultimately leads to a decrease in energy-efficiency. The 140 rpms recommendation when the leg is in contact with the ground does not imply the maximum rpms of the motor should be this. It is beneficial to have a motor with  
Figure 21: Peak power demand (**left**), and horizontal distance covered per joule consumed (**right**) when \(m=1\) kg, \(\omega=2\pi\) and varying leg radius. \begin{table}
\begin{tabular}{c||c|c|c|c|c} \hline  & **KE** & **GPE** & **Peak Power Demand** & **Distance Covered per Joule** \\ \hline \(\omega\) & Lineal & IND & E.I & M.D \\ \hline \(m\) & Lineal & Lineal & Lineal & I.P \\ \hline \(r\) & Lineal & Lineal & Lineal & I.P \\ \hline Small Impact & IND: Independent & Slight Impact & **M.D:** Moderate Decrease & Large Impact & **E.I:** Exponential Increase \\  & & & **M.D:** Moderate Decrease & **I.P:** Inversely Proportional. \\ \hline \end{tabular}
\end{table} 
Table 3: Angular velocity, mass, and leg radius effect on KE, GPE peak power demand and the distance covered per joule. maximum rpms over this, so it can move quicker in rotation angles, where the power demand is low and then slower when the power demand is higher. This will allow for better gait synchronization, which can increase the efficiency of the system. * **Increasing Maximum Speed:** If the maximum speed of the system wants to be increased, it might be worthwhile to increase the legs radius rather than selecting a motor with higher rpms. The desired maximum speed might be achieved with a larger leg that does not require a motor with so much power. On the other hand, this increase in leg radius will lead to more GPE and KE losses, but these losses will probably be smaller if this increase in leg radius has avoided choosing heavier motors. Moreover, the impact of the leg radius on the GPE and KE can be mitigated with gait synchronization. As previously said, these recommendations are for hexapod robots with no energy recovery. If energy is recovered when the power demand is negative, then the relationship between the different variables changes slightly.