Applied Bionics and Biomechanics

The structural bionicism of the knee joint of an automobile crash dummy is an important factor affecting the accuracy of the dummy’s knee displacement and knee flexion angle measurements in automobile crash tests. This study focused mainly on the optimization of the bionic structure of the knee joint of an automobile crash dummy to ensure that the dummy has a kinematic response closer to that of the knee joint of a real human. Forty sets of high-speed photographic images of the sphyrion were acquired by performing a trajectory-measurement test at the lower tibial point. Subsequently, the high-flexion motion trajectory of the knee joint was obtained by solving vector equations and by multicurve fitting. This trajectory, combined with the bionic structure design method, optimized the structure of the existing dummy’s knee joint. Thereby, its motion can be altered from a fixed-axis rotation to a non-fixed-axis curve motion close to how the human tibial plateau rotates around the femoral condyle. This increases the degrees of freedom of the dummy’s knee joint from two to three. The knee joint structures before and after the optimization were simulated kinematically using a multibody dynamics method. The results showed that the peak of the motion trajectory deviation of the optimized sphyrion decreased from 3.7% to 1.9%, and the average deviation decreased from 2.0% to 0.2%. This indicates that the structural optimization scheme improved the motion bionics of the crash dummy’s knee joint.

This paper describes a robotic system that uses an actively controlled glass to help patients with tremors. End-point control is proposed for the upper part of a robotic device that becomes active in response to motion changes or vibrations of its holder. The device mechanisms, hardware, software, and sensory system are all integrated, presenting a novel robotic glass design. The control system consists of two degrees of freedom proportional–integral velocity regulators for direct current motors. These regulators are designed, implemented, and tuned to keep the robotic glass stable against changes in its position. In realizing direct current motor control, it is essential to take system constraints into consideration to develop regulators that can handle the nonlinear Coulomb friction and avoid operating in the saturation zone. This is crucial when designing, tuning, and implementing regulators for real-time applications. The computer simulations of the system, which involved developing and running all the control algorithms for real-time applications, are carried out in Matlab/Simulink. The proposed designs are validated by comparing system simulations to real-time physical experiments. The recorded results confirmed the outstanding performance of the proposed experimental platform mechanisms and the accurate control tracking, which provides fast and precise control responses to meet the high requirements of a fast end-point control application.

Background. Though treatable, osteoporosis continues as a substantially underdiagnosed and undertreated condition. Bone mineral density (BMD) monitoring will definitely aid in the prediction and prevention of medical emergencies arising from osteoporosis. Although quantitative computed tomography (QCT) is one of the most widely accepted tools for measuring BMD, it lacks the contribution of bone architecture in predicting BMD, which is significant as aging progresses. This paper presents an innovative approach for the prediction of BMD incorporating bone architecture that involves no extra cost, time, and exposure to severe radiation. Methods. In this approach, the BMD is predicted using clinical CT scan images taken for other indications based on image processing and artificial neural network (ANN). The network used in this study is a standard backpropagation neural network having five input neurons with one hidden layer having 40 neurons with a tan-sigmoidal activation function. The Digital Imaging and Communications in Medicine (DICOM) image properties extracted from QCT of human skull and femur bone of rabbit that are closely associated with the BMD are used as input parameters of the ANN. The density value of the bone which is computed from the Hounsfield units of QCT scan image through phantom calibration is used as the target value for training the network. Results. The ANN model predicts the density values using the image properties from the clinical CT of the same rabbit femur bone and is compared with the density value computed from QCT scan. The correlation coefficient between predicted BMD and QCT density valued to 0.883. The proposed network can assist clinicians in identifying early stage of osteoporosis and devise suitable strategies to improve BMD with no additional cost.

Introduction. Lack of visual information in blind people during walking can affect the choice of muscle synergy from among the many incoming messages that reach the central nervous system (CNS). This study aimed to determine the effect of vision on the synergy of lower limb muscles during walking using the nonnegative matrix factorization algorithm (NNMF). Methods. Ten blind people and 10 people with normal vision participated in this study. Activities of involved muscles were recorded during walking. Muscle synergy matrix and synergy activation coefficient were calculated using the NNMF algorithm, while the variance accounted for criterion was used to determine the number of synergies required during walking. In order to assess the similarity of muscle synergy pattern and the relative weight of each muscle in each synergy in each group, Pearson correlation and independent samples t-test at a significance level of α ≤ 0.05 were used. Results. Four muscle synergies were extracted from EMG data during walking. The first (r = 0.431) and the second (r = 0.457) synergy patterns showed a moderate correlation between the two groups. However, the third (r = 0.302) and the fourth (r = 0.329) synergy patterns showed a weak correlation between the two groups. In the blind group, the relative weight of the muscles in the first synergy was significant for the external extensor muscle (), and in the second synergy for the biceps femoris. Also, in the third synergy, the relative weight was found to be significant in none of the muscles. In the fourth synergy, however, the relative weight of external extensor muscle in the blind group showed a significant decrease, as compared to the group with normal vision. Conclusions. These changes can be the strategy of the CNS to preserve the optimal functioning in the motor system of blind people.

Fish-like robot is a special autonomous underwater vehicle with broad application prospects. Some previous studies concentrated on the hydrodynamics of free-swimming fish-like robots. But the hydrodynamic performance of fish-like robot swimming with a tilt angle in constrained space has not been well studied, and the influence of environmental wave and current on its is also still unclear. In this paper, the experiment devices, including a physical fish-like robot, a hydrodynamics measurement platform, and a six-axis force sensor, are used to study the effect of attack angle and environmental condition on the hydrodynamics of near-surface swimming fish-like robot. Nine attack angles, five oscillating amplitudes, and three environmental conditions are analyzed in the experiments. It shows that thrust force decreases when caudal fin passes above water surface, but the increased difference between gravity force and buoyancy force will compensate the decreased force generated by caudal fin when fish-like robot swims with certain dive angle. The extra reaction force generated by solid bottom boundary will promote the thrust force and vertical force. The surface water wave condition or surface water current condition also has obvious effects on hydrodynamic performance. This paper provides a new perspective to the research on the hydrodynamic performance of fish-like robot and will do favor in the development of fish-like robot.

The magnesium alloy was made into orthopedic steel plates to repair tibial fractures of New Zealand white rabbits and to explore the biocompatibility, degradation behavior, and mechanical properties of the magnesium alloy plates in repairing fractures in vivo. Fifty-four rabbits were randomly divided into experimental, control, and sham-operated groups. Tibial fractures in the experimental and the control groups were fixed with magnesium alloy and titanium alloy plates, respectively, and only bone tunnels were established without any implants in the sham-operated group. The concentrations of serum alanine transaminase, creatinine (CREA), creatine kinase (CK), and magnesium ion were measured before and 1 day, 1, 2, 4, 8, and 16 weeks after operation, respectively, to evaluate the biocompatibility of magnesium alloy plates. The corrosion products and components were observed using a scanning electron microscope with an energy-dispersive spectroscopy system, and the corrosion rate was observed by weight loss testing. Then the degradation behavior of magnesium alloy plate was analyzed. Analysis of mechanical properties of magnesium alloy plates was done by four-point bending tests. There were no statistically significant differences in serum alanine transaminase, CREA, or CK at each time point among the three groups (). The degradation behavior of the magnesium alloy plates increased with the longer implantation time. The four-point bending test results indicated that the mechanical properties of magnesium alloy plates decreased gradually during the degradation. The results showed that magnesium alloy plates implanted into rabbit tibias degrade gradually with the implantation time, and the mechanical properties of the magnesium alloy weaken gradually during the degradation. Meanwhile, the magnesium alloy plate had excellent biocompatibility and biosafety in the process of degradation in vivo.