Search Results (23)

Humanoid robots have attracted considerable attention for their anthropomorphic structure, extended workspace, and versatile capabilities. This paper presents a novel humanoid upper-body robotic system comprising a pair of 8-degree-of-freedom (DOF) arms, a 3-DOF head, and a 3-DOF torso—yielding a 22-DOF architecture inspired by human biomechanics and implemented via standardized hollow joint modules. To overcome the critical reliance of zeroing neural network (ZNN)-based trajectory tracking on the Jacobian matrix derivative, we propose an integration-enhanced matrix derivative observer (IEMDO) that incorporates nonlinear feedback and integral correction. The observer is theoretically proven to ensure asymptotic convergence and enables accurate, real-time estimation of matrix derivatives, addressing a fundamental limitation in conventional ZNN solvers. Workspace analysis reveals that the proposed design achieves an 87.7% larger total workspace and a remarkable 3.683-fold expansion in common workspace compared to conventional dual-arm baselines. Furthermore, the observer demonstrates high estimation accuracy for high-dimensional matrices and strong robustness to noise. When integrated into the ZNN controller, the IEMDO achieves high-precision trajectory tracking in both simulation and real-world experiments. The proposed framework provides a practical and theoretically grounded approach for redundant humanoid arm control. Full article

Especially in real-world circumstances with uneven road surfaces and impulsive shocks, nonlinear dynamic effects in vehicle systems can greatly skew biometric data utilized to track passenger and driver physiological states. By creating a thorough multibody human–seat–chassis model, this work tackles the effect of vehicle-induced vibrations on the accuracy and dependability of biometric measures. The model includes external excitation from road-induced inputs, nonlinear damping between structural linkages, and vertical and angular degrees of freedom in the head–neck system. Motion equations are derived using a second-order Lagrangian method; simulations are run using representative values of a typical car and human body segments. Results show that higher vehicle speed generates more vibrational energy input, which especially in the head and torso enhances vertical and angular accelerations. Modal studies, on the other hand, show that while resonant frequencies stay constant, speed causes a considerable rise in amplitude and frequency dispersion. At speeds ≥ 50 km/h, RMS and VDV values exceed ISO 2631 comfort standards in the body and head. The results highlight the need to include vibration-optimized suspension systems and ergonomic design approaches to safeguard sensitive body areas and preserve biometric data integrity. This study helps to increase comfort and safety in both traditional and autonomous car uses. Full article

This paper presents a novel approach to developing control strategies for mobile robots, specifically the Pegasus, a bionic wheel-legged quadruped robot with unique chassis mechanics that enable four-wheel independent steering and diverse gaits. A multi-agent (MA) reinforcement learning (RL) controller is proposed, treating each leg as an independent agent with the goal of autonomous learning. The framework involves a multi-agent setup to model torso and leg dynamics, incorporating motion guidance optimization signal in the policy training and reward function. By doing so, we address leg schedule patterns for the complex configuration of the Pegasus, the requirement for various gaits, and the design of reward functions for MA-RL agents. Agents were trained using two variations of policy networks based on the framework, and real-world tests show promising results with easy policy transfer from simulation to the actual hardware. The proposed framework models acquired higher rewards and converged faster in training than other variants. Various experiments on the robot deployed framework showed fast response (0.8 s) under disturbance and low linear, angular velocity, and heading error, which was 2.5 cm/s, 0.06 rad/s, and 4°, respectively. Overall, the study demonstrates the feasibility of the proposed MA-RL control framework. Full article

Falls among the elderly have been a significant public health challenge, with severe consequences for individuals and healthcare systems. Traditional balance assessment methods often lack ecological validity, necessitating more comprehensive and adaptable evaluation techniques. This research explores the use of inertial measurement units to assess postural balance in relation to the Berg Balance Scale outcomes. We recruited 14 participants from diverse age groups and health backgrounds, who performed 14 simulated tasks while wearing inertial measurement units on the head, torso, and lower back. Our study introduced a novel metric, i.e., the volume that envelops the 3-dimensional accelerations, calculated as the convex hull space, and used this metric along with others defined in previous studies. Through logistic regression, we demonstrated significant associations between various movement characteristics and the instances of balance loss. In particular, greater movement volume at the lower back (p = 0.021) was associated with better balance, while root-mean-square lower back angular velocity (p = 0.004) correlated with poorer balance. This study revealed that sensor location and task type (static vs. dynamic) significantly influenced the coefficients of the logistic regression model, highlighting the complex nature of balance assessment. These findings underscore the potential of IMUs in providing detailed objective balance assessments in the elderly by identifying specific movement patterns associated with balance impairment across various contexts. This knowledge can guide the development of targeted interventions and strategies for fall prevention, potentially improving the quality of life for older adults. Full article

A head-related transfer function (HRTF) is a mathematical model that describes the acoustic path between a sound source and a listener’s ear. Using binaural synthesis techniques, HRTFs play a crucial role in creating immersive audio experiences through headphones or loudspeakers, using binaural synthesis techniques. HRTF measurements can be conducted either with standardised mannequins or with in-ear microphones on real subjects. However, various challenges arise in, for example, individual differences in head shape, pinnae geometry, and torso dimensions, as well as in the extensive number of measurements required for optimal audio immersion. To address these issues, numerous methods have been developed to generate new HRTFs from existing data or through computer simulations. This review paper provides an overview of the current approaches and technologies for generating, adapting, and optimising HRTFs, with a focus on physical modelling, anthropometric techniques, machine learning methods, interpolation strategies, and their practical applications. Full article

Our goal is to further understand how a simulated extravehicular mobility unit (xEMU) spacesuit affects the relative movement of one’s body segments. The effect of the xEMU spacesuit on gait is not yet fully understood. Here, gait was examined in terms of postural strategies, defined by the absolute angle with standard deviation (AAD) and the anchoring index (AI). The AAD values allowed the measurement of the absolute angles of body segments and their standard deviation, whereas the AI provided a measure of how stable a body segment was relative to a global reference frame and the inferior body segment. The body segments examined were the head, thorax, lumbar, and pelvis segments of 17 participants (26.53 ± 6.51 years old). The configurations tested included unsuited, or using a xEMU Vest or a hard upper body torso (HUT) for four walking conditions: eyes open/closed, with either forward or backward walking. The AAD values of the xEMU Vest were insignificant compared to those of the unsuited condition. The HUT significantly affected the AAD values compared to the unsuited condition. The AI for the HUT also indicates a new unique postural strategy being employed by the HUT group that was not previously observed. Full article

In self-driving vehicles, passengers can set their seats in an unconventional seating position, such as rear-facing. Sitting in such an orientation can increase the risk of whiplash in the head-and-neck system in a frontal impact, as frontal crashes usually have higher severities compared with rear-end crashes. This paper shows that a forward-facing front seat optimised for rear-impact protection needs to be redesigned to be used as a rear-facing seat. In the second and main part of this paper, a restraint system for rear-facing car seats is developed, and frontal impact simulations with 64 km/h of delta-V are used to evaluate its performance. The designed seating system comprises two rigid torso plates, a fixed recliner and an energy absorber under the seat pan. Without using the developed restraint system, the 50th percentile male human model is exposed to neck shear forces exceeding 600 N. With the developed restraint system, neck shear forces are less than 350 N in frontal impacts with 64 km/h of delta-V. Apart from whiplash, the risk of head, chest, lower extremity and lower back injuries are also evaluated. The results confirm that the developed restraint system successfully protects the occupant since all assessment criteria values are lower than the injury assessment reference values. Full article

Cartilage conduction is known widely as a third hearing transmission mechanism after the air and bone conduction methods, and transducers dedicated to the production of cartilage conduction sounds have been developed by several Japanese companies. To estimate the acoustic performance of the five cartilage conduction transducers selected for this study, both airborne sounds and cartilage conduction sounds were measured. Airborne sounds can be measured using a commercial condenser microphone; however, cartilage conduction sounds are impossible to measure using a conventional head and torso simulator (HATS), because the standard-issue ear pinna simulator cannot reproduce cartilage conduction sounds with the same spectral characteristics as the corresponding sounds measured in humans. Therefore, this study replaced the standard-issue simulator with a developed pinna simulator that can produce similar spectral characteristics to those of humans. The HATS manipulated in this manner realized results demonstrating that transducers that fitted the entrance to the external auditory canal more densely could produce greater cartilage conduction sounds. Among the five transducers under test, the ring-shaped device, which was not much larger than the entrance to the canal, satisfied the spectral requirements. Full article

The head-related transfer functions (HRTFs) describe the acoustic path transfer functions between sound sources in the free-field and the listener’s ear canal. They enable the evaluation of the sound perception of a human being and the creation of immersive virtual acoustic environments that can be reproduced over headphones or loudspeakers. HRTFs are strongly individual and they can be measured by in-ear microphones worn by real subjects. However, standardized HRTFs can also be measured using artificial head simulators which standardize the body dimensions. In this paper, a comparative analysis of HRTF measurement using in-ear microphones is presented. The results obtained with in-ear microphones are compared with the HRTFs measured with a standard head and torso simulator, investigating different positions of the microphones and of the sound source and employing two different types of microphones. Finally, the HRTFs of five real subjects are measured and compared with the ones measured by the microphones in the ear of a standard mannequin. Full article

Although hearing devices based on cartilage conduction have become more widely used in Japan, methods for evaluating the output volume of such devices have not yet been established. Although the output of air-conduction-based sound-generating devices (e.g., earphones and hearing aids) can be standardized via the head and torso simulator (HATS), this is not applicable to cartilage conduction devices because the simulated pinna is too soft (hardness: A5) compared with human aural cartilage. In this study, we developed polyurethane pinna that had the same shape but different degrees of hardness (A40, A20, and A10). We then compared the HATS results for the new pinna simulators with data from human ears. We found that the spectral shapes of the outputs increasingly approximated those of human ears as the simulated pinna hardness decreased. When a durometer was pressed against the ear tragus of a human ear, the hardness value ranged from A10 to A20. Accordingly, cartilage-conduction-based sound information could be obtained using a HATS that had a simulated pinna with a similar hardness value. Full article

This paper aims at providing an overview of the most used injury criteria (IC) and injury metrics for the study of the passive safety of vehicles. In particular, the work is focused on the injury criteria that can be adopted when finite element simulations and Human Body Models (HBMs) are used. The HBMs will result in a fundamental instrument for studying the occupant’s safety in Autonomous Vehicles (AVs) since they allow the analysis of a larger variety of configurations compared to the limitations related to the traditional experimental dummies. In this work, the most relevant IC are reported and classified based on the body segments. In particular, the head, the torso, the spine, the internal organs, and the lower limbs are here considered. The applicability of the injury metrics to the analyses carried out with the HBMs is also discussed. The paper offers a global overview of the injury assessment useful to choose the injury criteria for the study of vehicle passive safety. To this aim, tables of the presented criteria are also reported to provide the available metrics for the considered body damage. Full article

This study addressed an important but not yet thoroughly investigated topic regarding human exposure to radio-frequency electromagnetic fields (RF-EMF) generated by vehicular connectivity. In particular, the study assessed, by means of computational dosimetry, the RF-EMF exposure in road users near a car equipped with vehicle-to-vehicle (V2V) communication antennas. The exposure scenario consisted of a 3D numerical model of a car with two V2V antennas, each fed with 1 W, operating at 5.9 GHz and an adult human model to simulate the road user near the car. The RF-EMF dose absorbed by the human model was calculated as the specific absorption rate (SAR), that is, the RF-EMF power absorbed per unit of mass. The highest SAR was observed in the skin of the head (34.7 mW/kg) and in the eyes (15 mW/kg); the SAR at the torso (including the genitals) and limbs was negligible or much lower than in the head and eyes. The SAR over the whole body was 0.19 mW/kg. The SAR was always well below the limits of human exposure in the 100 kHz–6 GHz band established by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). The proposed approach can be generalized to assess RF-EMF exposure in different conditions by varying the montage/number of V2V antennas and considering human models of different ages. Full article

Headsets are increasingly used in the working environment. In addition to being frequently used by call-centre staff, they are also becoming more popular with remote workers and teleconference participants. The aim of this work was to describe and evaluate the acoustic signal parameters reproduced by headsets and examine the factors affecting the values of these parameters. The tests were carried out in laboratory conditions using a manikin (head and torso simulator) designed for acoustic research. A total of 12 headset models were tested during the research. The results show that the A-weighted sound pressure level of the test signal reproduced by four (100% gain) and two (75% gain) headsets exceeded 85 dB. The highest equivalent A-weighted sound pressure level was 92.5 dB, which means that the headset should not be used for more than approx. 1 h and 25 min; otherwise, the criterion value will be exceeded. The analysis of the acoustic signal reproduced by the headsets confirmed that the A-weighted sound pressure level affected the gain level in the test signal reproduction path. This value also depended on the type of connector used, the computer from which the test signal was reproduced and the type of sound card used. Full article

In the work environment, miniature electroacoustic transducers are often used in communication, for the transmission of warning signals or during training. They can be used in headphones or mounted in personal protective equipment. It is often important to reproduce sounds accurately. The purpose of this work was to assess audio strips by comparing the frequency response of the signal in the electrical outputs of six common-purpose devices. Based on the risk of hearing damage, the level of noise exposure was assessed. The following headphones were investigated: low-budget closed-back, open-back for instant messengers, open-back for music, and in-ear. A head and torso simulator with a transfer function was used. The most uniform shape of the frequency response of the signal at the electrical outputs was found to be in smartphones. Sound cards integrated into laptop motherboards had highly unequal characteristics (up to 23 dB). In the case of one of the laptops, the upper range of the transmitted frequencies was limited to the 12,500 Hz band. An external sound card or wireless headphones can improve the situation. In the worst-case scenario, i.e., rock music, the listening time was limited to 2 h and 18 min. Full article

Because cartilage conduction—the transmission of sound via the aural cartilage—has different auditory pathways from well-known air and bone conduction, how the output volume in the external auditory canal is stimulated remains unknown. To develop a simulator approximating the conduction of sound in ear cartilage, the vibrations of the pinna and sound in the external auditory canal were measured using pinna simulators made of silicon rubbers of different hardness (A40, A20, A10, A5, A0) as measured by a durometer. The same procedure, as well as a current calibration method for air conduction devices, was applied to an existing pinna simulator, the Head and Torso Simulator (hardness A5). The levels for vibration acceleration and sound pressure from these pinna simulators show spectral peaks at dominant frequencies (below 1.5 kHz) for the conduction of sound in cartilage. These peaks were likely to move to lower frequencies as hardness decreases. On approaching the hardness of actual aural cartilage (A10 to A20), the simulated levels for vibration acceleration and sound pressure approximated the measurements of human ears. The adjustment of the hardness used in pinna simulators is an important factor in simulating accurately the conduction of sound in cartilage. Full article