Ground Reaction Force Control in the UGent Knee Rig

The concept of FAIR data (Findable, Accessible, Interoperable and Reusable) is well-known in orthopedic research. With this notion in mind, the validated UGent Knee Rig (UGKR) is extended to facilitate ground reaction force (GRF) control. The bench mark system in dynamic knee rigs is the Oxford Knee Rig which is the basis of many knee rigs in literature. It has the intrinsic quality of imposing a constant ground reaction force on a specimen. A new control strategy is introduced to extend the functionality of the UGKR with GRF control. It consist of a model-based control strategy with feedback and gain adaptation based on model identification. The presented control strategies are tested on mechanical hinges and cadaver specimens to verify its performance. The results show that the presented control strategies are capable of meeting the control specification of a force error less than 10 N as reported in literature. This innovation allows for comparison between groups working on dynamic knee rigs on an international level resulting in a more unified platform for data comparison.