# Framework for Developing Bio-Inspired Morphologies for Walking Robots
## 7 Discussion  
The framework for developing bio-inspired morphologies proved to be a great help as a tool for developing the ALPHA, and ensured a prototype that replicates the biological morphology to a high extent (Table 1). In [15] the morphology of dung beetles was applied to simulations to investigate its advantages in hexapods. However, by using bio-inspired development, a greater level of detail in replicating the biological morphology has been achieved with the ALPHA hexapod (Figure 2b), together with a more quantitative investigation of the insect morphology. Further research of the framework in the near future will be needed, including more use cases. Here, the presented framework can be used as the basis for further research into bio-inspired morphologies. An analysis investigating performance parameters (Table 4) showed that the anchor morphology of ALPHA created an improved performance compared to a template morphology. The simulated template leg was limited to shorter steps (Section 6.1), as its DOF2 motor quickly reached the maximum output, due a poor distribution of loads between the three motors (Figure 9). The DOF2 motor carried 2.7 to 3.0 times the load of the DOF1 and DOF3 motors combined. The DOF1 motor carried nearly no load, as the leg's mass force vector was parallel to its rotary axis. Meanwhile, the anchor leg's improved distribution of torque loads on all three motors enabled 50.0% greater reach before either the DOF1 or DOF2 motor were overloaded. Here, the DOF2 motor was the first overloaded motor when reaching in the posterior direction, while the DOF1 motor was overloaded in the anterior direction. Hence, the anchor's improved distribution of torque loads on the motors enables greater step lengths, more movement options in the path, and thereby a greater _movement versatility_ (Section 6.1). Figure 14: Accelerations of the three motors during a gait cycle for both the template and anchor morphology. Figure 13: The motors’ torque during gait cycles for both (**a**) template and (**b**) anchor morphology. From Figure 9 it can be derived that the anchor's stride length can be further increased with 0.07 m of forward reach for every newton meter that the DOF1 motor's torque capacity is increased. This can be continued to the leg's maximum forward reach of 0.30 m, when the DOF1 motor output is increased to 6.59 Nm (+37.3%). It is plausible that the robot's volume and mass will not be drastically increased by upgrading the DOF1 motors. Furthermore, this highlights an advantage of the anchor morphology. It is more feasible to upgrade the anchor's usable step length than it is to upgrade the template's. The anchor obtains full reach by improving the DOF1 motors' torque output to the 6.59 Nm, while the template needs to improve the DOF2 motors to 7.63 Nm (+59.0%). Furthermore, it is harder to upgrade the DOF2 motors, as they are positioned on the legs' moving frame, where larger volumes will restrict movement, and greater masses increase inertia. The DOF1 motors are more proximal than the DOF2 motors and attach directly to the body structure, which makes it easier to change them without affecting the leg movements. A trade-off for the anchor's higher mobility is slightly higher power consumption (Figure 11). In addition, the anchor morphology's improved torque distribution enables 95.5% greater reach, by utilizing a greater amount of its forward work envelope (79.6%) than the template morphology (45.8%) (Figure 12). The template morphology was able to reach the highest point of 0.36 m. However, it is prevented from practically using this isolated position, as the DOF2 motor will be overloaded as soon as the leg starts to pull downwards from the position, thereby moving the leg in a forward curve (0.24 m and beyond). The positions throughout this curve will overload the DOF2 motor, as the end-effector reaches too far from the origin point. It can be considered that the load on the front legs might be reduced in some positions and angles of the hexapod body, which can enable greater reach.