# A Synthetic Nervous System Controls
## 4 Discussion and Future Work
### Walking Comparison between SimRoach2 and a Cockrach  
The main goal of this work was to develop a design method for an insect model actuated with an antagonistic pair of muscles. To show that the design method works, walking data was collected and presented. In this section, the data from SimRoach2 is compared to a cockroach.  
It is important to note that the cockroach kinematic data was not used during the design process. We did not design our model to \"match\" this data. We believe that the walking data of our model and a cockroach are similar is because of the detailed work that went into the many different parts of this model and because the model was informed by the biomechanics and nervous system of the animal. These results are a consequence of our process, and the fact that there are some similarities suggest that this model captures some of the underlying principles.  
When commanded to walk forward, SimRoach2 walks straight after reaching steady state (Figure 10). The exact path of the body does include some side to side wobble, but this is also seen in cockroaches [55]. It is interesting to note that in SimRoach2, there is no correction mechanism to alter the path against error. The straight walking path is a result of the completeness of the design method in this paper. In the future, we will apply our work on directional stepping with MantisBot [60] to SimRoach2, giving us a complete-body model with which we can develop a model of the central complex, a region of the brain implicated in the control of walking speed and direction [11].  
The walking speed of SimRoach2 is just below 20 cm/s (Figure 10). This is similar to cockroach data presented in [61] for free walking. The pitch and roll of a walking cockroach were measured to be between \(\pm 4\) degrees and \(\pm 7\) degrees, respectively [55]. SimRoach2 walks with pitch rotations just slightly outside these limits and with roll rotations well within these limits (Figure 11). Again, we believe that our results are similar to that of a cockroach because of the detailed work that went into many different parts of SimRoach2, and this similarity will serve as a launching point for future studies on locomotion.  
Joint Angle Comparison  
For most joints in SimRoach2, the positions of the AEP and PEP appear to match fairly well, especially compared to the range of motion of these joints (Figures 12-14), suggesting that the change between stance and swing phase happens at similar positions in each leg. The means of the data sets were also compared using statistical \(t\)-tests. Of the 30 tests on the AEP and PEP for the 15 joints, 20 of the tests showed a statistically significant difference between the animal and animat. It is difficult to know if the model needs to capture these small details to inform neurobiology or robotics. Past studies of insect locomotion have focused on the changes in individual joints' range of motion between different conditions [14; 27]. As we increase the complexity of SimRoach2's locomotion, we plan to take a similar approach; not focusing as much on how the joint kinematics match the animal, as much as how they change in different scenarios. We believe such changes help reveal what parameters the nervous system is controlling during locomotion.