Bearing Seat Vibration Modes Undergoing Unbalanced Excitation of Multirotating Drums

Transmission modes of multiple rotating parts on combine harvester are complex and diverse, which resulted in large vibration and poor stability when the entire machine is harvesting. Aiming at the complex vibration problem of the combine harvester threshing system, this paper established the dynamic response model of the multidrum parallel system under different transmission modes and solved the vibration characteristics of the system. An experiment on the axial unbalance response of the parallel drum system under different transmission modes was carried out. The results show that the internal units of the threshing system form a whole through the transmission system, which causes the unbalanced response of the system to be superimposed on parallel threshing drums, thereby increasing the vibration amplitude. In addition, the change of the transmission mode will cause the vibration transmission path in the system to change greatly, and the boundary conditions of the system will be changed at the same time, which will eventually lead to the change of the unbalanced response characteristics.

Textronics spacer knitted material tests as a key element of the diagnostic system that monitors above the proper level of seat vibration

This research is focused on the construction and examination of a prototype of a spacer knitted material with integrated sensors. The combination of textiles with elements of electronics, computer science, and a knowledge of automation is called textronics. This type of material has been proposed as a component of diagnostic systems to monitor the extension level of vibration in employee seats at selected workstations or in children’s chairs. The purpose of the diagnostic system is to improve personal protective equipment (PPE) and increase employee safety. The spacer knitted material was tested with vibration frequencies in the range of 0–40 Hz to develop metrological properties under reproducible and repeatable conditions. The tested spacer knitted material meets the requirements of sensory properties such as vibration. The tested material is characterized by the following metrological parameters: total uncertainty U = 4.5%, sensitivity Sa = 0.64 [V/s2/m] and excitability threshold of 5 Pa with simultaneous high coefficient of low-frequency vibration damping of effective amplitude transmissibility (SEAT) = 2.3. Spacer knitted materials are modern constructs that enable the creation of new hybrid structures that have other properties, e.g., sensory suppression, in addition to spatial form.

Effect of delayed resonator on the vibration reduction performance of vehicle active seat suspension

The combination of dynamic vibration absorber and partial state feedback with time-delay is called delayed resonator. In order to suppress the seat vibration caused by uneven road surface and improve ride comfort, the delayed resonator is applied to the seat suspension to realize active control of the seat suspension system. The dynamic model of the half-vehicle suspension system is established, and the time-delay differential equation of the system under external excitation is solved by the precise integration method. The root mean square of the time-domain vibration response of seat displacement, seat acceleration and vehicle acceleration are selected as the objective function. Then, the optimal time-delay control parameters are obtained by particle swarm optimization algorithm. The frequency sweeping method is used to obtain the critical time-delay value and time-delay stable interval of the system. Finally, an active seat suspension model with delayed resonator is established for numerical simulation. The results show that the delayed resonator can greatly suppress the seat vibration response regardless of the road simple harmonic excitation or random excitation. Compared with dynamic vibration absorber, it has a better vibration absorption effect and a wider vibration reduction frequency band.

Evaluating the Efficacy of Multi-Sensory Stimulations on Simulator Sickness and Sense of Presence during HMD-mediated VR Experience

Virtual reality (VR) is currently being used for a wide range of applications. However, a sense of discomfort during VR experiences (commonly referred to as simulator sickness), is an obstacle for acceptance of the technology outside the niche of tech enthusiasts. Some lines of evidence have shown that sensory input, especially related to vestibular stimulation, may reduce the symptoms related to simulator sickness and increase the sense of presence. This investigation aims at understanding how mechanical vibration can be used to improve user experience in VR, reducing symptoms of simulator sickness and increasing the sense of presence. Four different groups comprising a total of 80 participants were tested under different conditions of sensory input (visual and vibratory, visual and auditory, visuo-auditory and vibratory, and visual only), during a VR roller-coaster experience. A questionnaire was used as the research instrument to evaluate both the sense of presence and the degree of simulator sickness experienced in VR. No significant differences in simulator sickness or presence were found between the groups exposed to seat vibration and/or audio. However, female participants experienced higher sense of presence when vibration was included. For participants experiencing a high degree of simulator sickness, vibration improved the experienced sense of presence, and the inclusion of vibration (but not sound) decreased the level of sickness-related disorientation. The inclusion of multi-sensory stimulation in VR revealed possibilities to improve the experience in some user categories; however, the use of vibration stimulation requires further research to be proven effective for the general public.Keywords: virtual reality, simulator sickness, presence, HMDs, vibration