Sensorless Power Assistance Control for a Lumbar Assist Device This paper presents a sensorless control for humanxe2x80x99s lumbar power assistance by our developed lumbar assist device (LAD). The proposed sensorless control is realized by a disturbance observer and an extended admittance model. The disturbance observer is developed to estimate the torque that the wearer applies to the lumbar assist device, and the extended admittance model is adopted to generate the target angular velocity of the lumbar assist device. The power assistance experiments with our LAD are conducted. The effect of the power assistance evaluated by EMG signal and heart rate shows that the wearerxe2x80x99s burden is decreased by about 8% and 10%, respectively. These results show that the proposed sensorless control for lumbar power assistance is effective.

Performance Analysis of Torquesensorless Assist Control of a Powered Exoskeleton Using Highly Backdrivable Actuators For human motion support, there is an active focus on research and development of powered exoskeletons. A powered exoskeleton is directly fitted to the human body; thus, it is necessary to consider the safety of the humanrobot interaction, including improving the backdrivability. Toward this problem, a powered exoskeleton that uses a highly backdrivable reduction gearbox even at a high reduction ratio is proposed, and a userxe2x80x99s external force can be estimated without using a torque sensor even though the system has very high total gear ratio of 408.57:1. This paper investigated the apparent mechanical impedance of an exoskeleton during assist control execution and examined the performance and operability of the assist control. Finally, a questionnaire of participants was conducted and the mechanical impedance that resulted in a high operability was examined by implementing admittance control.