Sit-to-stand and stand-to-sit assistance for paraplegic patients with CUHK-EXO exoskeleton

Bing Chen, Chun Hao Zhong, Hao Ma, Xiao Guan, Lai Yin Qin, Kai Ming Chan, Sheung Wai Law, Ling Qin*, Wei Hsin Liao

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

17 Citations (Scopus)


In this paper, we introduce a lower extremity exoskeleton CUHK-EXO that is developed to help paraplegic patients, who have lost the motor and sensory functions of their lower limbs to perform basic daily life motions. Since the sit-to-stand and stand-to-sit (STS) motion is the first step for paraplegic patients toward walking, analysis of the exoskeleton's applicability to the STS motion assistance is performed. First, the human-exoskeleton system (HES) is modeled as a five-link model during the STS motion, and the center of pressure (COP) on the ground and center of gravity of the whole system are calculated. Then, a description of the CUHK-EXO hardware design is presented, including the mechatronics design and actuator selection. The COP position is an important factor indicating system balance and wearer's comfort. Based on the COP position, a trajectory online modification algorithm (TOMA) is proposed for CUHK-EXO to counteract disturbances, stabilize system balance, and improve the wearer's comfort in the STS motion. The results of STS motion tests conducted with a paraplegic patient demonstrate that CUHK-EXO can provide a normal reference pattern and proper assistive torque to support the patient's STS motion. In addition, a pilot study is conducted with a healthy subject to verify the effectiveness of the proposed TOMA under external disturbances before future clinical trials. The testing results verify that CUHK-EXO can counteract disturbances, and help the wearer perform the STS motion safely and comfortably.

Original languageEnglish
Pages (from-to)535-551
Number of pages17
Issue number4
Publication statusPublished - 1 Apr 2018

Scopus Subject Areas

  • Control and Systems Engineering
  • Software
  • Mathematics(all)
  • Modelling and Simulation
  • Mechanical Engineering
  • Computer Science Applications
  • Control and Optimization

User-Defined Keywords

  • Balance control
  • Lower extremity exoskeleton
  • Motion assistance
  • Sit-to-stand
  • Stand-to-sit
  • Trajectory generation


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