Where Should I Look Optimised Gaze Control for Whole-Body Collision Avoidance in Dynamic Environments

Motion control in dynamic environments is one of the most important problems in using mobile robots in collaboration with humans and other robots. In this paper, the motion control of a four-Mecanum-wheeled omnidirectional mobile robot (OMR) in dynamic environments is studied. The robot’s differential equations of motion are extracted using Kane’s method and converted to discrete state space form. A nonlinear model predictive control (NMPC) strategy is designed based on the derived mathematical model to stabilize the robot in desired positions and orientations. As a main contribution of this work, the velocity obstacles (VO) approach is reformulated to be introduced in the NMPC system to avoid the robot from collision with moving and fixed obstacles online. Considering the robot’s physical restrictions, the parameters and functions used in the designed control system and collision avoidance strategy are determined through stability and performance analysis and some criteria are established for calculating the best values of these parameters. The effectiveness of the proposed controller and collision avoidance strategy is evaluated through a series of computer simulations. The simulation results show that the proposed strategy is efficient in stabilizing the robot in the desired configuration and in avoiding collision with obstacles, even in narrow spaces and with complicated arrangements of obstacles.

Download Full-text

Tai Chi and vestibular rehabilitation effects on gaze and whole-body stability

Journal of Vestibular Research ◽

10.3233/ves-2004-14605 ◽

2004 ◽

Vol 14 (6) ◽

pp. 467-478 ◽

Cited By ~ 3

Author(s):

Chris A. McGibbon ◽

David E. Krebs ◽

Steven L. Wolf ◽

Peter M. Wayne ◽

Donna Moxley Scarborough ◽

...

Keyword(s):

Significant Relationship ◽

Postural Stability ◽

Intervention Program ◽

Tai Chi ◽

Vestibular Rehabilitation ◽

Whole Body ◽

Gaze Control ◽

Gaze Stability ◽

Vestibular Hypofunction ◽

The Relationship

Tai Chi (TC) is a comparatively new intervention for peripheral vestibular hypofunction, which is often treated with vestibular rehabilitation (VR). We compared gaze stability (GZS), whole-body stability (WBS) and footfall stability (FFS) during locomotion among 26 people with vestibulopathy (VSP), randomized into two treatment arms (13 TC and 13 VR). Each intervention program was offered for 10 weeks. GZS improved more for VR than for TC, but WBS (and FFS) improved more for TC than for VR. There was a significant relationship between changes in GZS and WBS for the VR subjects (r = 0.60, p = 0.01), but not for TC subjects. There was a significant relationship between changes in WBS and FFS for both VR (r = 0.65, p < 0.01) and TC (r = 0.58, p = 0.02) groups; the relationship disappeared in the VR but not the TC group when controlling for GZS. These findings suggest that VR and TC both benefit patients with VSP but via differing mechanisms. Moreover, these data are the first to test the assumption that improving gaze control among patients with VSP perforce improves postural stability: it does not. We conclude that GZS is most improved in those who receive VR, but that TC improves WBS and FFS without improving GZS, suggesting patients with VSP can rely on non-gaze related mechanisms to improve postural control.

Download Full-text