# Grasp Analysis for the Robot-Based Manipulation of Pre-Assembled Cables with Electrical Connectors
## 5 Discussion
### Limitations and Potential Solution Approaches  
The presented methodology is subject to the boundary conditions and assumptions of the contact model developed by [11]. In Section 2.1, its most important aspects were presented. In addition, the model underlies other influencing factors, such as the mesh resolution of the contact surfaces. The authors show that the error rate decreases sharply as the number of triangular mesh elements increases and, for example, is less than 4% for 300 triangular mesh elements [11]. Moreover, during experimental testing, external force disturbances along the grasp axis were not evaluated by the authors [11].  
Additionally, the same uniform pressure distribution is used for all WPs in this work. Theoretically, the accuracy of the grasp force estimation could be further increased by performing finite element analysis to determine the pressure distribution at each WP. However, this would require high manual effort, which is not compatible with the objective of this work. Determining a specific pressure distribution for each WP using a contact model would also be difficult in advance since the six cable wrench components are individually combined for each WP. Thus, the use of the same pressure distribution for all WPs seems to be a suitable compromise.  
For the results of the plug used in this work, the contact model for NSCs is also applied to planar contacts; compare surface pairs 1 and 3. The results for the pure mating force for surface pairs 1 and 3, for example, match the analytical calculation exactly. In general, further investigation is needed to determine the effect of possible fitting errors of the 6 DLS model when applied to planar contacts. If the fitting error exceeds a specific threshold, a planar contact model could be applied to these.  
Furthermore, the friction coefficient is often subject to variation in reality [4], and, therefore, its lower limit should be used [11]. Moreover, possible deformations of thegripper jaws during grasping are not taken into account. These depend on the topology of the gripper jaws to be designed.  
In addition, in the reference scenario, we have assumed the mating force to be simplified in the axial direction. The modeling of this force has to be adapted depending on the intended mating strategy. As shown by [15], further forces and torques can occur during mating. In our framework, their values could be added to the external wrench of WP 16* in the EC coordinate system. If mating is performed by an external device at the gripper, such as a lifting cylinder, the mating force does not have to be applied--in this case, only the cable wrenches operate.  
Moreover, the cables are currently generated in a straight line in the physics simulation scenario. The generation of curved cable shapes could be implemented with the procedure described in [37]. In addition, the trajectories are currently referenced to the CCI coordinate system and must first be adjusted by the offset to the selected surface pair for use on the robot.  
In summary, the courses in this paper are subject to a number of superimposing uncertainties. The courses should, therefore, be regarded as a possibility for comparative estimation. It is, therefore, essential to consider ordinary safety factors in the required grasp force. The introduced reference scenario of interconnecting battery modules is to be seen as a synthetically generated example for the purpose of the investigations in this work. The dimensions of parts, the combinations of cable instances and ECs, and the position of the CCI, etc., are not based on real product specifications.