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ImprovIng post-stroke Crossed roller Bearing TheraPy exoskeleTal roBo


Physical therapy is key during


the first few days after a stroke in order to help patients


re-learn how to use their limbs. Here, IKO explains why its


CRBH and CRBF crossed roller bearings were selected for Harmonic Bionics’ exoskeleton


A


pproximately 700,000 people survive strokes each year in the US alone. This number is expected to increase by


around 40% over the course of the next 10 years. However, with deaths caused by strokes decreasing, and more and more of us predicted to live longer, healthier lives, the importance and reliance on rehabilitation is only going to increase. With this being the case, traditional post-stroke rehabilitation techniques will simply not be enough.


an eXoskeletal robot Improves phYsICal therapY oUtComes For stroke sUrvIvors


The first few days after a stroke are key to enabling a patient to re-learn how to use limbs that are often paralysed as a result. This often starts with physical therapy in the intensive care unit. Effective therapy must be based on the


principles of neuromuscular physiology and can often take advantage of known neurological coupling between human joints, using coordinated movements and forces to boost true functional recovery. Shoulder rehabilitation is regarded as one of


8 DESIGN SOLUTIONS MARCH 2023


the most challenging forms of physical therapy, due to the complexity and range of motion (RoM) of the shoulder, which poses a significant obstacle to traditional forms of therapy. The Harmony exoskeleton from Harmonic Bionics has been designed to specifically handle these challenges. This presents a highly sensitive and repeatable platform which can greatly improve the effectiveness of shoulder therapy for stroke survivors. Harmonic Bionics was founded in 2016 to


develop innovative rehabilitation robotics platforms for the clinical market. Their Harmony exoskeleton wraps around the patient’s shoulders, arms and wrists and can power their joints to assist patients as they perform various dynamic movement tasks. This helps them relearn the specific rhythm


that happens between the shoulder’s girdle and its ball and socket joint to maximize range of motion, thereby correcting the impaired neuromuscular function. Whereas a physical therapist helps a patient


move their arm and observes the movement, the exoskeleton creates an assist-as-needed paradigm that encourages active patient participation and frees up the therapist to massage the arm or even monitor multiple


patients at once. The platform intends to promote better, more effective healing and improve outcomes for both the patient and the hospital. The rehabilitation robot uses advanced actuator


technology and a suite of sensors that collect motion data, at a high speed of two kilohertz, which is fed into an algorithm to give users responsive control of varying levels of resistance during exercises. The designers needed a roller bearing that could carry large moment loads so the exoskeleton can move coaxially with the patients’ skeletal structure as they move their arms. This enables bimanual therapy which takes advantage of a proven neurological coupling of the left and right halves of the human nervous system to aid recovery. The bearing also needed to be small, lightweight and offer a low coefficient of friction (CoF). An exoskeleton like this has unique


challenges and limited operating space. IKO’s CRBH and CRBF crossed roller bearings were an obvious choice.


CrosseD roller bearIngs CarrY hIgh moment loaDs to assIst patIents anD therapIsts


IKO’s crossed roller bearings are both compact and rigid, making them well-suited for robotics


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