Assistive robot for standing with physical activity estimation based on muscle arrangements of human legs

A physical activity estimation scheme is proposed for patients who use a robot for standing assistance. In general, conventional assistive robots do not require patients to use their own physical strength to stand, which leads to decreased strength of the elderly. Therefore, an assistive robot that maximally uses a patient's remaining physical strength is desired. The assistive robots can achieve this objective by estimating the physical activity of the patient when they stand. The activity estimation proposed here is primarily based on a human musculoskeletal model of a lower limb, which exhibits a biarticular muscle function. The patient generates a natural standing motion using the biarticular muscle function, and the proposed model enables the assistive robot to estimate the patient's physical activity, without using biosensors, such as electromyographs, which are normally stuck on patients. The proposed estimation is implemented with a prototype assistive robot that assists elderly patients to use their remaining physical strength based on the estimated results, thus testing the effectiveness of the proposed method.