  Numerous diseases and aging can cause degeneration of people's balance
ability resulting in limited mobility and even high risks of fall. Robotic
technologies can provide more intensive rehabilitation exercises or be used as
assistive devices to compensate for balance ability. However, With the new
healthcare paradigm shifting from hospital care to home care, there is a gap in
robotic systems that can provide care at home. This paper introduces Mobile
Robotic Balance Assistant (MRBA), a compact and cost-effective balance
assistive robot that can provide both rehabilitation training and activities of
daily living (ADLs) assistance at home. A three degrees of freedom (3-DoF)
robotic arm was designed to mimic the therapist arm function to provide balance
assistance to the user. To minimize the interference to users' natural pelvis
movements and gait patterns, the robot must have a Human-Robot Interface(HRI)
that can detect user intention accurately and follow the user's movement
smoothly and timely. Thus, a graceful user following control rule was proposed.
The overall control architecture consists of two parts: an observer for human
inputs estimation and an LQR-based controller with disturbance rejection. The
proposed controller is validated in high-fidelity simulation with actual human
trajectories, and the results successfully show the effectiveness of the method
in different walking modes.
