Carbon fiber running-specific prostheses (RSPs) have allowed individuals with lower extremity amputation (ILEA) to participate in running. It has been established that as running speed increases, leg stiffness (Kleg) remains constant while vertical stiffness (Kvert) increases in able-bodied runners. The Kvert further depends on a combination of the torsional stiffnesses of the joints (joint stiffness; Kjoint) and the touchdown joint angles. Thus, an increased understanding of spring-like leg function and stiffness regulation in ILEA runners using RSPs is expected to aid in prosthetic design and rehabilitation strategies. The aim of this study was to investigate stiffness regulation to various overground running speeds in ILEA wearing RSPs. Eight ILEA performed overground running at a range of running speeds. Kleg, Kvert and Kjoint were calculated from kinetic and kinematic data in both intact and prosthetic limbs. Kleg and Kvert in both limbs remained constant when running speed increased, while intact limbs in ILEA running with RSPs have a higher Kleg and Kvert than residual limbs. There were no significant differences in Kankle, Kknee and touchdown knee angle between the legs at all running speeds. Hip joints in both legs did not demonstrate spring-like function; however, distinct impact peaks were observed only in the intact leg hip extension moment at early stance phase, indicating that differences in Kvert between limbs in ILEA are due to attenuating shock with the hip joint. Therefore, these results suggest that ILEA using RSPs have a different stiffness regulation between the intact and prosthetic limbs during running.

Carbon fiber running-specific prostheses (RSPs) have allowed individuals with lower extremity amputation (ILEA) to actively participate in sporting activities including competitive sports. In spite of this positive trait, the RSPs have not been thoroughly evaluated regarding potential injury risks due to abnormal loading during running. Vertical impact peak (VIP) and average loading rate (VALR) of the vertical ground reaction force (vGRF) have been associated with running injuries in able-bodied runners but not for ILEA. The purpose of this study was to investigate vGRF loading in ILEA runners using RSPs across a range of running speeds. Eight ILEA with unilateral transtibial amputations and eight control subjects performed overground running at three speeds (2.5, 3.0, and 3.5 m/s). From vGRF, we determined VIP and VALR, which was defined as the change in force divided by the time of the interval between 20 and 80% of the VIP.We observed that VIP and VALR increased in both ILEA and control limbs with an increase in running speed. Further, the VIP and VALR in ILEA intact limbs were significantly greater than ILEA prosthetic limbs and control subject limbs for this range of running speeds. These results suggest that 1) loading variables increase with running speed not only in able-bodied runners, but also in ILEA using RSPs, and 2) the intact limb in ILEA may be exposed to a greater risk of running related injury than the prosthetic limb or able-bodied limbs.

In this paper, we propose a flexible three-axial tactile sensor array for measuring both normal and shear loads. The sensor array has 16 tactile sensor units based on piezoresistive strain gauge. It is constructed on a Kapton polyimide film using advanced polymer micromachining technologies. Thin metal strain gauges are embedded in polyimide to measure normal and shear loads, which are tested by applying forces from 0 to 1 N. The developed sensor unit had a hysteresis error of about 9% and repeatability error of about 1.31%. The sensor showed a good resulting image when pressed by a circle-shaped object with 10 N loads. The proposed flexible three-axial tactile sensor array can be applied in a curved or compliant surface that requires slip detection and flexibility, such as a robotic finger.

This paper presents the design of robot foot module of four-point biped walking robot and its fabrication. The foot module has four sensor units based on contact-resistance force sensor. The thin-film-type force sensor is fabricated by coating resistive ink on thin polyimide film using silk screening technique. The simple structure is devised and fabricated to assemble the thin force sensor rigidly. The unit force sensor module is evaluated by the calibration setup to obtain the characteristics of repeatability and hysteresis. The sensor module presents hysteresis error of about 5% and repeatability error of about 0.37%. The calculated zero moment point (ZMP) of the foot module is also compared with the measured position using static load of 50 N. The maximum location error of ZMP is less than 10%. The robot foot module shows the possibility of applying it to humanoid walking.

This paper describes the design and fabrication of a flexible tactile sensor using polymer micromachining technologies, which can measure the three-component force and temperature caused by thermal conductivity. The tactile sensor is comprised of sixteen micro force sensors with 4 x 4 arrays and its size being 13 mm x 18 mm. Each micro force sensor has a square membrane, and its force capacity is 0.6 N in the three axis directions. The normal and shear forces are obtained from four thin-film metal strain gauges embedded in a polyimide thin-film membrane. The optimal positions of the strain gauges are determined by the strain distribution obtained form finite element analysis. In order to acquire force and temperature signals simultaneously from the fabricated tactile sensor, we fabricated a PCB based on multiplexer, operational amplifier and microprocessor with CAN network function. The fabricated flexible tactile sensor was evaluated from the evaluation apparatus. Also we confirmed that the sensor has the function of temperature sensing throughout feasibility test such as contacting with some objects. I.