A Hardware-in-the-loop Simulation Study of a Mechatronic System for Anterior Cruciate Ligament Injuries Rehabilitation

One of the main ligaments of the knee is the Anterior Cruciate Ligament (ACL), which is critical to maintain stability and regular gait patterns. Moreover, the knee is the most complex and largest joint in the human body. There are many traditional methods and devices to assist therapy. Nevertheless, there are several research studies in robotic platforms for lower limb rehabilitation. This paper presents a hardware-in-the-loop (HIL) simulation of a movement control algorithm for mechatronic-assisted rehabilitation based on exercises and movements associated with therapies for ACL injuries. The implementation of the algorithm was conducted using a computational model in order to test the mechatronic system Nukawa without having to use the actual robot. Several tests were performed in order to validate the mathematical model of Nukawa. In order to assess whether the implemented HIL simulator works properly for ACL rehabilitation exercises, a physiotherapist performed six exercises and the movements were recorded with a commercial acquisition device, these trajectories were conducted to the HIL simulator. The Integral-Square-Error (ISE) was computed for each test, and since it was small, it may be despised. Therefore, the motion control algorithm is able to manipulate the three joints at the same time, hence it is possible to follow specific trajectories. In addition, the mean execution time M = 11.5 ms and the standard deviation SD = 3.9 taken by the controller is smaller than the sampling period, therefore we proposed that this system can be tested in real-time, without notable delays related to the movement control algorithm.