In this paper, the effect of wear in the fluid film journal bearings on the dynamic behavior of rotor bearing system has been studied depending on the analytical driven of dynamic stiffness and damping coefficients of worn journal bearing. The finite element method was used to modeling rotor bearing system. The unbalance response, critical speed and natural frequency of rotor bearing system have been studied to determine the changes in these parameters due to wear. MATLAB software was used to find the analytical values of dynamic coefficients of journal bearing. The results of rotor mounted on fluid film journal bearings showed that the wear in journal bearing increases the amplitude of unbalance response and decrease critical speed, stability and the natural frequencies.  

No abstract

This paper proposes robust control for three models of the linear inverted pendulum (one mass linear inverted pendulum model, two masses linear inverted pendulum model and three masses linear inverted pendulum model) which represents the upper, middle and lower body of a bipedal walking robot. The bipedal walking robot is built of light-weight and hard Aluminum sheets with 2 mm thickness. The minimum phase system and non-minimum phase system are studied and investigated for inverted pendulum models. The bipedal walking robot is programmed by Arduino microcontroller UNO. A MATLAB Simulink system is built to embrace the theoretical work. The results showed that one linear inverted pendulum is the worst performance, worst noise rejection and the worst set point tracking to the zero moment point. But two masses linear inverted pendulum models and three masses linear inverted pendulum model have a better performance, a better high-frequency noise rejection characteristic and better set-point tracking to the zero moment point.

Due to the varied needs of persons who have lost a lower limb in their everyday lives, ankle-foot prosthetic technology is continually evolving. Numerous prosthetic ankles have been created in recent years to restore the ankle function of lower limb amputees. Most ankle foot prostheses, on the other hand, are passive, such as the solid ankle cushion heel and the energy storage and release foot (ESAR). The solid ankle foot can only provide steady vertical support during ambulation; however, the ESAR foot can store energy and gradually release it throughout human walking periods, hence increasing the walking pace of amputees. The aim of this work is to describe the design and manufacture of an actuated ankle-foot prosthesis. The main benefit of powered ankles is that they are capable of mimicking natural stride, particularly in steep or uneven terrain conditions. The primary objective is to establish two degrees of freedom of ankle rotation in two planes, plantar flexion and dorsiflexion in the sagittal plane, besides inversion and eversion in the frontal plane. As software can improve the gait stability, an automatic modifiable transmission arrangement was prepared for delivering the current design motions in the sagittal plane based on empirical collected biomechanical data related to passive prosthetic normal gait circumstances. However, the ankle rolling in the frontal plane was guided mechanically by means of mono leaf spring. The majority of the ankle mechanical components are made of 7075-T6 aluminum alloy and are integrated onto ESAR carbon fiber laminated foot. For a unilateral above-knee amputee, the ankle function at self-selected walking was assessed, achieving maximum results of 10° inversion, 10° eversion, 12° plantar flexion and 18° dorsiflexion ankle angles. Also, the patient gait experiment in a normal cadence showed an improvement in plantar flexion behavior for the powered ankle in contrast with the passive ankle

In this paper, the effect of wear in the fluid film journal bearings on the dynamic stability of rotor bearing system has been studied depending on the development of new analytical equations for motion, instability threshold speed and steady state harmonic response for rotor with offset disc supported by worn journal bearings. Finite element method had been used for modeling the rotor bearing system. The analytical model is verified by comparing its results with that obtained numerically for a rotor supported on the short bearings. The analytical and numerical results showed good agreement with about 8.5% percentage error in the value of critical speed and about 3.5% percentage error in the value of harmonic response. The results obtained show that the wear in journal bearing decrease the instability threshold speed by 2.5% for wear depth 0.02 mm and 12.5% for wear depth 0.04 mm as well as decrease critical speed by 4.2% and steady state harmonic response amplitude by 4.3% for wear depth 0.02 mm and decrease the critical speed by 7.1% and steady state harmonic response amplitude by 13.9% for wear depth 0.04 mm.