3D ground reaction force (GRF) estimation during walking is important for gait and inverse dynamics analyses. Recent studies have estimated 3D GRF based on kinematics measured from optical or inertial motion capture systems without force plate measurement. A neural network (NN) could be used to estimate ground reaction forces. The NN network approach based on segment kinematics requires the selection of optimal inputs, including kinematics type and segments. This study aimed to select optimal input kinematics for implementing an NN for each foot’s GRF estimation. A two-stage NN consisting of a temporal convolution network for gait phase detection and a gated recurrent unit network was developed for GRF estimation. To implement the NN, we conducted level/inclined walking and level running on a force-sensing treadmill, collecting datasets from seven male participants across eight experimental conditions. Results of the input selection process indicated that the center of mass acceleration among six kinematics types and trunk, pelvis, thighs, and shanks among 15 individual segments showed the highest correlations with GRFs. Among four segment combinations, the combination of trunk, thighs, and shanks demonstrated the best performance (root mean squared errors: 0.28, 0.16, and 1.15 N/kg for anterior-posterior, medial-lateral, and vertical components, respectively).

This study aimed to determine mechanisms involved in the decrease of knee adduction moment (KAM) when waking with a contralateral cane without any constraint. Ten young subjects performed walking under two conditions: unassisted (no cane) or with a cane. After collecting data from the stance phase of the left foot, kinematic and kinetic data at early and late peaks of KAM were extracted for further analyses. When using a cane, early and late peaks of KAM decreased (p < 0.05) by 20.5% and 29.6%, respectively. Stepwise multiple regression analysis showed that the moment arm accounted for 59% and 95% of the variance of early and late KAM peaks, respectively. This reduction in moment arm occurred primarily due to lateral rotation of the GRF. Regarding the mechanism behind this, it could be due to the following: 1) by using a cane, the synthetic center of pressure shifted medially, which caused synthetic GRF to become more vertical than that of an unassisted walking and accordingly, and 2) the decrease of horizontal component of synthetic GRF reduced horizontal component of foot GRF, leading to lateral rotation of foot GRF. Understanding these mechanisms might help us improve effective use of canes.

In this study, an insole-type ground reaction force (GRF) measurement system using a load cell was manufactured and configured as a system that can measure joint angle and GRF, when walking in conjunction with a commercialized inertial sensor. The data acquisition device was used to acquire synchronized data, between the inertial measurement unit (IMU) sensor and the load cell insole. A three-dimensional motion analysis system comprising six infrared cameras and two ground reaction forces, was used to check the accuracy of the gait measurement system, comprising an inertial sensor and a load cell insole. The motion and force data were acquired while performing five times six-meter walking test by five young adult male subjects (Age: 26.0±1.8, Height: 171.4±6.8 cm, Weight: 62.2±10.8 kg). It was measured and as a result of comparing the calculated sagittal joint angle with the vertical GRF, the sagittal lower extremity joint angle correlation coefficient (Pearson’s r) was 0.40 to 0.94, and the vertical GRF to be 0.98 to 0.99. It is necessary to upgrade the joint angle calculation algorithm through future research. Additionally, the possibility of clinical application for actual stroke patients will be reviewed.

In this study, the fracture characteristics of structural adhesives were investigated according to the shape of a DCB and TDCB by using the FEM. First, to obtain the reliability of the finite element method, the experimental and FEM analyses were compared, and the reliability was secured. When the graph of reaction force to displacement on the TDCB test specimen was examined, it was found that the smaller the slope, the stronger the exhibited property sustaining the load to the end of the adhesive surface. Maximum reaction force occurred was just before the adhesive was removed. The shear stress of the specimen exhibited the same characteristics and an equivalent stress. Thus, the data of this study resulting in the fracture characteristics of the structural adhesives for each shape can be applied to the design with durability.

The residual vibration during the high acceleration and deceleration of a motion stage degrades the manufacturingsystem productivity and lifespan. Although a passive RFC mechanism with a movable magnet track reduces the residual vibration of the system base, a magnet track resonance may occur according to the motion profile, and the mover inposition error increases due to the residual vibration of the magnet track. We investigated input-shaping methods for a linear motor motion stage with a passive RFC mechanism. An air-bearing linear motor motion stage with the passive RFC mechanism is built, and the dynamic characteristic of the passive RFC mechanism is identified using a freevibration test. Then, mover velocity profiles are generated using various input-shaping methods. Further, the effects of the input-shaping methods on the air-bearing linear motor motion stage are investigated by comparing the magnet track oscillation, settling time, and mover in-position error. Finally, several input-shaping methods are applied to reduce the mover rise-time delay for the proposed linear motor motion stage. A properly shaped input motion profile removes the residual vibration of the passive RFC mechanism without any additional devices, as well as reducing the transmitted reaction force and the in-position error.

Recently, Laser Direct Imaging (LDI) has been used to replace lithography in Flexible Printed Circuit Board (FPCB) manufacturing. However, repeated motion of a linear motor caused residual vibration in the granite on which the workpiece was placed when the motor either accelerated or decelerated. Because the residual vibration made positioning less accurate, there were more defective products and worse productivity. This paper proposes a way to reduce vibration in the granite during the precision stage. First, the frequency domain of the vibrations of a pneumatic vibration isolator is identified. Second, we present the design of the mechanism using a voice coil actuator and a capacitive displacement sensor. Third, we apply a feedback control algorithm based on PID to cancel displacement. Consequently, we are able to propose an optimal way to reduce vibration for the laser direct imaging equipment. The amount of vibration reduction is evaluated in terms of amplitude and settling time.