No abstract

No abstract

Weight and power consumption of variable stiffness actuation mechanism are critical for its implementation in a portable assistive device combined with an actuator, gearhead, elastic element, and batteries. Therefore, we present a portable stiffness modulation mechanism for an Ankle Foot Orthosis (AFO) utilizing pneumatic stiffness. The mechanism consists of two units: a driving unit that controls an air pump and an AFO unit that performs free motion and stiffness modulation functions. The actuation from the driving unit to the AFO unit via pneumatic hose makes the effective weight of the device light compared to the direct driven device at the ankle joint. We derived a mathematical model of the stiffness modulation to determine the pressure required. In order to control the required stiffness according to the gait phases, a threshold-based gait phase detection algorithm was implemented, employing ground reaction force sensor signals from heel and forefoot. The effectiveness of the proposed AFO was validated by the experiments in a patient with foot drop, performing walking with and without AFO actuation.

Involuntary movements such as heart beating in surgical environment and surgeon's tremor disturb a micro surgical manipulation and cause a risk of patient wound. Although the delicate operation is performed by a skilled surgeon, the sensitivity of the surgeon is limited to quantify the range of safe contact forces. In this paper, we developed a compact hand-held surgical device to maintain a required contact force to maintain a required contact force using a custom force sensor and a linear delta mechanism. The custom optical force sensor measured the contact force of the device tip and the linear delta mechanism compensated undesired forces to maintain a consistent contact force. The proposed device is consisted of force sensing unit and actuating unit. The device was improved from our previous Linear Delta mechanism based prototype in terms of size, weight, and force sensing capability. The developed device was validated by investigation of contact force accuracy in a fixed condition and a hand-held condition. In hand-held condition, the visual feedback of the current contact force was provided, and the performance of the contact force regulation was investigated by comparing the root mean square (RMS) contact force errors and standard deviation in with and without control cases. The fluctuation (less than 50 mN) of the force regulation control of the device showed the feasibility of the device for the use in delicate operations.

No abstract