Multilink cable-driven manipulators offer the compactness of serial mechanisms while benefitting from the advantages of cable-actuated systems. One major challenge in modeling multilink cable-driven manipulators is that the number of combinations in the possible cable-routing increases exponentially with the number of rigid bodies. In this paper, a generalized model for multilink cable-driven serial manipulators with an arbitrary number of links that allow for arbitrary cable routing is presented. Introducing the cable-routing matrix (CRM), it is shown that all possible cable routing can be encapsulated into a single representation. The kinematics and dynamics for the generalized model are derived with respect to the CRM. The advantages of the proposed representation include the simplicity and convenience in modeling and analysis, where all cable routing is inherently considered in a single model. To illustrate this, the inverse dynamics analysis is performed for two example systems: a 2-link 4-DoF manipulator that is actuated by 6 cables and an 8-link 24-DoF mechanism actuated by 76 cables. The results show the validity and scalability of the generalized formulation, allowing for complex systems with arbitrary cable routing to be modeled and analyzed.

This paper presents a force observer that estimates the external interaction forces from the measured joint position and joint actuation for a class of robotic manipulators. This is done without an explicit (physical) force or torque sensor, through an extended state observer (ESO) assuming a known model of the dynamics of the manipulator. It is designed to be capable of estimating relatively fast time-varying external forces. The main result shows that the proposed ESO is theoretically able to estimate unknown time-varying external forces to an arbitrary accuracy for any initial condition starting in a given compact set. Simulation results demonstrate the effectiveness of the proposed ESO. Moreover, first experimental evaluations with a healthy subject and a post-stroke patient on a rehabilitation robotic platform show the feasibility of the approach in this context and highlight the importance of the quality of the dynamic model.

The thumb of a natural hand or a prosthetic hand plays a significant role in realizing a hand's grasping and manipulation activities. This requires that mechanical design of a prosthetic hand should allow its thumb to perform both abduction/adduction and flexion/extension in order to mimic a natural hand's grasping and manipulation abilities with a minimum number of actuators. In this work, we propose a novel monolithic soft robotic thumb for an anthropomorphic and transradial prosthetic hand. The thumb and the whole prosthetic hand were fabricated using a low cost 3D printing technique, with sizes comparable to those of real human ones but with much lighter weights. Based on the concepts of soft robotics and underactuation, the thumb shows significant mechanical compliance and performs well in power grasps, precision grasps and lateral grasps of different shaped and sized household objects. The soft thumb which has two modes of operation based on an innovative and compact mechanism, and one actuator only offers grasping versatility (capable of both abduction/adduction and flexion/extension). This novel thumb minimizes the number of actuators and reduces the corresponding requirement on space consumption (for housing its actuators) and power consumption, which are favorable features to develop low cost, low power and low weight prosthetic hands with intrinsic compliance.

SUMMARY: Miniaturized surgical devices are promising for the future development of minimally invasive and endoluminal surgery. However, the dexterity and therapeutic functions of these devices are limited. In this paper, a reconfigurable modular robotic system is proposed to perform screening and interventions in the gastrointestinal tract. In the proposed system, millimeter-sized robotic modules are ingested and tasked to assemble into an articulated mechanism in the stomach cavity. The modules are assembled according to the target location to perform precise intervention. Based on this concept, a preliminary report is presented covering the robotic schemes for the endoluminal reconfigurable platform, the design with structural functions, the control strategy, and the interval-based constraint satisfaction algorithm to determine the suitable topologies of the reconfigurable robot for the given task.