Asymptotically Stable Walking of a Five-Link Underactuated 3D Bipedal Robot

This paper presents three feedback controllers that achieve an asymptotically stable, periodic, and fast walking gait for a 3D (spatial) bipedal robot consisting of a torso, two legs, and passive (unactuated) point feet. The contact between the robot and the walking surface is assumed to inhibit yaw rotation. The studied robot has 8 DOF in the single support phase and 6 actuators. The interest of studying robots with point feet is that the robot's natural dynamics must be explicitly taken into account to achieve balance while walking. We use an extension of the method of virtual constraints and hybrid zero dynamics, in order to simultaneously compute a periodic orbit and an autonomous feedback controller that realizes the orbit. This method allows the computations to be carried out on a 2-DOF subsystem of the 8-DOF robot model. The stability of the walking gait under closed-loop control is evaluated with the linearization of the restricted Poincar\'e map of the hybrid zero dynamics. Three strategies are explored. The first strategy consists of imposing a stability condition during the search of a periodic gait by optimization. The second strategy uses an event-based controller. In the third approach, the effect of output selection is discussed and a pertinent choice of outputs is proposed, leading to stabilization without the use of a supplemental event-based controller

How patients contribute to an online psychoeducation forum for bipolar disorder: a virtual participant observation study

Background: In a recent exploratory randomized controlled trial, an online psychoeducation intervention for bipolar disorder has been found to be feasible and acceptable to patients and may positively impact on their self-management behaviors and quality of life. Objective: The objective of the study was to investigate how these patients contribute to an online forum for bipolar disorder and the issues relevant for them. Methods: Participants in the intervention arm of the Bipolar Interactive PsychoEDucation (“BIPED”) trial were invited to contribute to the Beating Bipolar forum alongside receiving interactive online psychoeducation modules. Within this virtual participant observation study, forum posts were analyzed using thematic analysis, incorporating aspects of discourse analysis. Results: The key themes which arose from the forum posts included: medication, employment, stigma, social support, coping strategies, insight and acceptance, the life chart, and negative experiences of health care. Participants frequently provided personal narratives relating to their history of bipolar disorder, life experiences, and backgrounds, which often contained emotive language and humor. They regularly sought and offered advice, and expressed encouragement and empathy. The forum would have benefitted from more users to offer a greater support network with more diverse views and experiences. Conclusions: Online forums are inexpensive to provide and may offer peer support and the opportunity for patients to share their experiences and explore issues related to their illness anonymously. Future research should focus on how to enhance patient engagement with online health care forums