Vision-Based Hybrid Controller to Release a 4-DOF Parallel Robot from a Type II Singularity

The high accuracy and dynamic performance of parallel robots (PRs) make them suitable to ensure safe operation in human–robot interaction. However, these advantages come at the expense a reduced workspace possible appearance type II singularities. latter is due loss control PR requires further analysis keep stiffness even after singular configuration reached. All or subset limbs could be responsible for singularity, they can detected by using angle between two output twist screws (OTSs). this has not been applied because it an accurate measure pose PR. This paper proposes new hybrid controller release 4-DOF from singularity based on real time vision system. system data are used automatically readapt moving identified OTSs. intended knee rehabilitation PR, results show how accomplished with smooth controlled movements where patient’s safety compromised.