Design of a multi-axis full body haptic device including four commercial robotic arms

Over the last twenty years, rehabilitation robotics has undergone continuous growth as an emerging field with the aim of adding automation to rehabilitation treatments. The elderly and stroke patients are two of the largest groups of the population that experience limited ability of motion. In order to sustain the autonomy of subjects experiencing locomotory limitations and lower their reliance on classic assistive devices or human help, many physical assistance robotic devices are being developed to aid in a variety of therapeutic support tasks. These devices, more commonly referred to as rehabilitation robots, are mechatronic systems aimed to reinstate some level of motor function in a patient. The technological advancement of robotic devices in the field has played a key role in several improvements in rehabilitation practices due to their ability to give support with the necessary physical exertion and high repetition of exercises. Our research offers a new potential design for a robotic rehabilitation system, including four commercial robotic arms, capable of high-speed motion for both upper and lower limbs at a reduced cost compared to the current market available systems, which are commonly based on proprietary components. From the computation of the human limb and robotic manipulator workspaces alignment employing the Iterative Closest Point algorithm, which supported a precise selection of the adequate commercial robotic arms, a novel procedure that allows a visual validation of the overlapping is proposed. The workspaces acquired and represented in the format of point clouds are converted into virtual solid structures, as non-uniform rational b-spline curves, compatible with most common CAD and 3D modeling software, and are connected to the primary joints of a 95-percentile human mannequin which is uploaded in the finite prototype of the system allowing a real-time validation of the manipulators positioning in space. A structural steel frame capable of supporting the high maximum inversion torque of the lower manipulators, with minimal floor anchoring points and two cantilever pedestals to support the upper manipulators are developed ad-hoc. In the study, great importance is given to frame validation steps, performing Finite Element Analysis and Harmonic Analysis with the goal of assessing the rigidity of the structure, taking into account the millimetric maximum displacement constraint which is required for a consistent control strategy for the application. The initial design of a mechatronic haptic chair, including direct kinematic and frame concept with static validation, that can provide stability to the human subject during rehabilitation, is proposed selecting a PRR open-loop structure with 3 degrees of freedom as opposed to the employment of a 6 degrees of freedom closed-loop Stewart platform, commonly deployed in haptic entertainment applications. The design leaves necessary free space at the bottom of the seat, avoiding cluttering the lower limbs workspaces and allowing gait analysis. The elaborate presents preliminary laboratory results to confirm the viability of the use of industrial arms due to their control rate unconformity with respect to standard haptic application requirements along with validation of the initial control scheme and propose rehabilitation viability tests for future research.