OBJECTIVE: We present an algorithm that enables percutaneous needle-placement procedures to be performed with unencoded, unregistered, minimally calibrated robots while removing the constraint of placing the needle tip on a mechanically enforced Remote Center of Motion (RCM) MATERIALS AND METHODS: The algorithm requires only online tracking of the surgical tool, a five-degree-of-freedom (5-DOF) robot comprising three prismatic DOF, two rotational DOF An incremental adaptive motion control cycle guides the needle to the insertion point, also orients it to align with the target-entry-point line The robot executes RCM motion without having a physically constrained fulcrum point RESULTS: The proof-of-concept prototype system achieved 0 78 mm translation accuracy, 1 4 degrees rotational accuracy (this is within the tracker accuracy) within 17 iterative steps (0 5-1 s) CONCLUSION: This research enables robotic assistant systems for image-guided percutaneous procedures to be prototyped/constructed more quickly, less expensively than has been previously possible Since the clinical utility of such systems is clear, has been demonstrated in the literature, our work may help promote widespread clinical adoption of this technology by lowering system cost, complexity