Cable-driven parallel manipulators (CDPM) potentially offer many advantages over serial manipulators, including greater structural rigidity, greater accuracy, and higher payload-to-weight ratios. However, CDPMs possess limited moment resisting/exerting capabilities and relatively small orientation workspaces. Various methods have been contemplated for overcoming these limitations, each with its own advantages and disadvantages. The focus of this paper is on one such method: the addition of base mobility to the system. Such base mobility gives rise to kinematic redundancy, which needs to be resolved carefully in order to control the system. However, this redundancy can also be exploited in order to optimize some secondary criteria, e.g., maximizing the size and quality of the wrench-closure workspace with the addition of base mobility. In this work, the quality of the wrench-closure workspace is examined using a tension-factor index. Two planar mobile base configurations are investigated, and their results are compared with a traditional fixed-base system. In the rectangular configuration, each base is constrained to move along its own linear rail, with each rail forming right angles with the two adjacent rails. In the circular configuration, the bases are constrained to move along one circular rail. While a rectangular configuration enhances the size and quality of the orientation workspace in a particular rotational direction, the circular configuration allows for the platform to obtain any position and orientation within the boundary of the base circle. Furthermore, if the bases are configured in such a way that the cables are fully symmetric with respect to the platform, a maximum possible tension-factor of one is guaranteed. This fully symmetric configuration is shown to offer a variety of additional advantages: it eliminates the need to perform computationally expensive nonlinear optimization by providing a closed-form solution to the inverse kinematics problem, and it results in a convergence between kinematic singularities and wrench-closure singularities of the system. Finally, we discuss a particular limitation of this fully symmetric configuration: the inability of the cables to obtain an even tension distribution in a loaded configuration. For this reason, it may be useful to relax the fully symmetric cable requirement in order to yield reasonable tensions of equal magnitude.

Assisted motor therapies play a critical role in enhancing functional musculoskeletal recovery and neurological rehabilitation. Our long term goal is to assist and automate the performance of repetitive motor-therapy of the human lower limbs. Hence, in this paper, we examine the viability of a light-weight and reconfigurable hybrid (articulatedmultibody and cable) robotic system for assisting lowerextremity rehabilitation and analyze its performance. A hybrid cable-actuated articulated multibody system is formed when multiple cables are attached from a ground-frame to various locations on an articulated-linkage based orthosis. Our efforts initially focus on developing an analysis and simulation framework for the kinematics and dynamics of the cable-driven lower limb orthosis. A Monte Carlo approach is employed to select configuration parameters including cuff sizes, cuff locations, and the position of fixed winches. The desired motions for the rehabilitative exercises are prescribed based upon motion patterns from a normative subject cohort. We examine the viability of using two controllers -a joint-space feedback linearized PD controller and a task-space force-control strategy -to realize trajectory-and path-tracking of the desired motions within a simulation environment. In particular, we examine performance in terms of (i) coordinated control of the redundant system; (ii) reducing internal stresses within the lowerextremity joints; and (iii) continued satisfaction of the unilateral cable-tension constraints throughout the workspace. A c c e p t e d M a n u s c r i p t N o t C o p y e d i t e d Downloaded From: http://mechanismsrobotics.asmedigitalcollection.asme.org/ on 01/05/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use Alamdari 2 A c c e p t e d M a n u s c r i p t N o t C o p y e d i t e d Downloaded From: http://mechanismsrobotics.asmedigitalcollection.asme.org/ on 01/05/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use Journal of Mechanisms and Robotics.A c c e p t e d M a n u s c r i p t N o t C o p y e d i t e d Downloaded From: http://mechanismsrobotics.asmedigitalcollection.asme.org/ on 01/05/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use Journal of Mechanisms and Robotics.A c c e p t e d M a n u s c r i p t N o t C o p y e d i t e d Downloaded From: http://mechanismsrobotics.asmedigitalcollection.asme.org/ on 01/05/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use Journal of Mechanisms and Robotics.A c c e p t e d M a n u s c r i p t N o t C o p y e d i t e d Downloaded From: http://mechanismsrobotics.asmedigitalcollection.asme.org/ on 01/05/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use Journal of Mechanisms and Robotics.A c c e p t e d M a n u s c r i p t N o t C o p y e d i t e d Downloaded From: http://mechanismsrobotics.asmedigitalcollection.asme.org/ on 01/05/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use Alamdari 7 A c c e p t e d M a n u s c r i p t N o t C o p y e d i t e d Downloaded From: http://mech...

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This paper examines the design, analysis and control of a novel hybrid articulated-cable parallel platform for upper limb rehabilitation in three dimensional space. The proposed lightweight, low-cost, modular reconfigurable parallel-architecture robotic device is comprised of five cables and a single linear actuator which connects a six degrees-of-freedom moving platform to a fixed base. This novel design provides an attractive architecture for implementation of a home-based rehabilitation device as an alternative to bulky and expensive serial robots. The manuscript first examines the kinematic analysis prior to developing the dynamic equations via the Newton-Euler formulation. Subsequently, different spatial motion trajectories are prescribed for rehabilitation of subjects with arm disabilities. A low-level trajectory tracking controller is developed to achieve the desired trajectory performance while ensuing that the unidirectional tensile forces in the cables are maintained. This is now evaluated via a simulation case-study and the development of a physical testbed is underway.