The number of people with a mobility disorder caused by stroke, spinal cord injury, or other related diseases is increasing rapidly. To improve the quality of life of these people, devices that can assist them to regain the ability to walk are of great demand. Robotic devices that can release the burden of therapists and provide effective and repetitive gait training have been widely studied recently. By contrast, devices that can augment the physical abilities of able-bodied humans to enhance their performances in industrial and military work are needed as well. In the past decade, robotic assistive devices such as exoskeletons have undergone enormous progress, and some products have recently been commercialized. Exoskeletons are wearable robotic systems that integrate human intelligence and robot power. This paper first introduces the general concept of exoskeletons and reviews several typical lower extremity exoskeletons (LEEs) in three main applications (i.e. gait rehabilitation, human locomotion assistance, and human strength augmentation), and provides a systemic review on the acquisition of a wearer's motion intention and control strategies for LEEs. The limitations of the currently developed LEEs and future research and development directions of LEEs for wider applications are discussed.

SUMMARY: 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.

To improve the energy efficiency and downsize the powered ankle-foot prostheses (PAFP) but still provide sufficient instantaneous power output, elastic actuators (EAs) are widely used. Generally, there are two kinds of EAs: series elastic actuator (SEA), and parallel elastic actuator (PEA). Both of them can reduce the energy requirement and peak power of the motor in the PAFP by using elastic elements to store and release energy during walking cycles. Researchers working on prostheses fields have been focusing on the design of PAFP driven by SEAs. As a result, several PAFP driven by SEAs were proposed. Compared with the PAFP driven by SEAs, the PAFP driven by PEAs could have more benefits, such as lower copper loss and higher force bandwidth due to the smaller motor output torque requirement. In this paper, we aim at designing a PAFP driven by a PEA. Based on the energy requirement analysis, an energy-efficient PAFP is proposed. The designed PAFP can mimic human intact ankle with the minimum energy consumption that equals to the human ankle net positive work. Besides, with the motor output torque being decreased, the motor peak power of the PAFP is reduced by 64%.

This article presents a review of the application of insole plantar pressure sensor system in recognition and analysis of the hemiplegic gait in stroke patients. Based on the review, tailor made 3D insoles for plantar pressure measurement were designed and fabricated. The function is to compare with that of conventional flat insoles. Tailor made 3D contour of the insole can improve the contact between insole and foot and enable sampling plantar pressure at a high reproducibility.

In this paper, we reported innovative design of a lower extremity exoskeleton developed by The Chinese University of Hong Kong (CUHK-EXO) that can help the paralyzed individuals to regain the ability to stand up/sit down (STS) and walk. CUHK-EXO is developed with the features of ergonomic design, user-friendly interface and high safety. The CUHK-EXO hardware design including mechanical structure, electrical system, and multiple sensors is introduced first. A pair of smart crutches and smart phone App are designed as part of the human-machine interface, which can improve the intelligence of the system and make the exoskeleton easier to be used by physical therapists and paralyzed patients. Then, the CUHK-EXO control is developed with STS motion assistance. Finally, pilot trial study is conducted for a healthy subject, and testing results show that the developed CUHK-EXO can help the subject perform desired STS motions.