ZeroG: Overground gait and balance training system

1
ZeroG Overground gait and balance training
system

• Joseph Hidler, PhD David Brennan, MBE iian
  Black, MBE Diane Nichols, PT Kathy Brady, MSPT
  Tobias Nef, PhD

2

• Study Aim
• Present ZeroG, a new overground, body-weight
  support (BWS) system that helps patients practice
  safe and controlled gait, balance, and postural
  activities.
• Relevance
• Incorporating BWS into gait therapy allows
  patients to safely practice high number of steps.
  
• Current BWS gait training often restricted to
  treadmill because of limitations with
  commercially available systems.

3
Design

• ZeroG
• Provides both static and dynamic BWS.
• Rides along overhead track, allowing practice
  while using walking aids and walking on flat
  surfaces, rough terrain, or stairs.
• Uses active trolley system that automatically
  follows patients as they walk, so they feel
  vertical unloading forces but very little
  horizontal forces.

(a) Side and (b) top view of ZeroG illustrating
custom-series elastic actuator that controls rope
force. Top and bottom assemblies have been
removed from (b) for clarity. DC direct current.
4
Experimental Tests

• System maintained constant forces, producing much
  more normal ground reaction forces.

• Active trolley minimized horizontal forces
  experienced by patient during gait.

Subject descended approximately 16 in. with level
of unloading set to 30 lb.
(a) Desired movement speeds 20, 40, 60 in./s
(0.5, 1.0, 1.5 m/s). (b) Resulting rope angle
averaged over 10 trials.
5
Conclusions

• Performance of custom-series elastic actuator and
  trolley tracking was well within original design
  goals.
• Training with ZeroG will allow patients to
  practice activities critical to functional
  independence at home and in community.