# System for Evaluation and Compensation of Leg Length Discrepancy for Human Body Balancing
## 6 Conclusions  
In this paper, a new methodology for the Evaluation and Compensation of LLD for Human Body Balancing is presented. For this purpose, a mechatronic system with two 3-RPS parallel manipulators comprising moving force plates with adjustable height and angles was developed. The mathematical model of the system was described in detail and a virtual simulation model in Matlab was created. To balance the human body standing on the force plates, a novel algorithm (HBBA) was developed and tested on a virtual simulation model and the mechatronic system. Two simulation models, namely the human body model with LLD and scoliosis, are described in the paper and tested by simulation. In both cases, the HBBA achieved an equalization of leg load distribution. Figure 21: Experiment 3: (**a**) \(CoM_{x}\), the position of the human body’s CoM; (**b**) reference height of the left (\(z_{Lref}\)) and right (\(z_{Rref}\)) force plate, current height of the left (\(z_{L}\)) and right (\(z_{R}\)) force plate; (**c**) the load on the left (\(m_{L}\)) and right (\(m_{R}\)) leg; (**d**) the balancing trigger signal (\(Q\)) marking the start of a new HBBA iteration; and (**e**) left and right force plate height difference (\(\Delta z\)), which corresponds with the LLD evaluation (\(\Delta I\)) in the HBBA’s final step. To validate the new mechatronic system, leg load distribution measurements were conducted on 46 volunteers. The obtained results show that people without evident LLD have asymmetric load distribution on their legs. Thus, it is important to include a vision system in the process of estimating LLD so that measurements of the location of predefined anatomical points are taken into account for the final diagnosis. While conducting the experiments, it was noticed that the relation between the shift in height difference (\(\Delta_{z}\)) and corresponding change in the CoM varies with the BMI, mass and posture of a patient. This fact will be used in the future for the creation of an adaptation algorithm for the weight parameter of the HBBA. Finally, the HBBA was tested on a volunteer with simulated LLD. It was experimentally shown that the HBBA compensated the volunteer's simulated LLD and balanced their body. The developed mechatronic system enables the leveling of the pelvis by changing the height of the platforms a subject is standing on, which is a significant improvement in terms of the technical aspect, duration and patient experience when compared to the standing on blocks measuring method. In future work, tests will be done with the HBBA on persons who have both LLD and scoliosis. Based on promising results, presented herein, we received funds under Proof-of-Concept program from Croatian agency HAMAG BICRO for clinical trials on 35 patients that already started and we hope to have clinical results in the next 18 months. Furthermore, the fact that the force plates' angle can be altered opens up the possibility of creating an algorithm that can correct excessive pronation and supination. Additionally, the developed mechatronic system can be used for rehabilitation and therapeutic purposes, with the aim of working out the joints and thus helping a patient achieve the desired range of motion. Conceptualization, Z.V., K.O., A.M., H.K. and S.B. ; Formal analysis, Z.V., K.O., H.K. and S.B. ; Methodology, Z.V. and S.B. ; Project administration, J.N. and A.M.; Software, Z.V. and J.N. ; Supervision, H.K. and S.B. ; Validation, Z.V. and K.O. ; Writing--original draft, Z.V. and S.B. ; and Writing--review and editing, Z.V. and S.B. This research was funded as part of the pre-seed capital program Proof of Concept (PoC) by HAMAG-BICRO, Croatia. The authors declare no conflict of interest.