Research on dynamic load characteristics and active control strategy of electro-mechanical coupling powertrain of drum shearer cutting unit under impact load

In order to extend the service life of the long-chain gear transmission system of a drum shearer, an electro-mechanical coupling model of a drum shearer cutting unit is established. The model considers the dynamic characteristics of the motor, time-varying meshing stiffness, as well as the drum load characteristics. Additionally, the dynamic characteristics and control strategy for suppressing the dynamic load of the gear transmission system under impact load are investigated based on this model. Firstly, the influence of the gear transmission system of the drum shearer cutting unit under impact load is analyzed. Then, on that basis, the active control strategy based on motor torque compensation is proposed to suppress the dynamic load of the gear transmission system caused by mutational external load. Finally, the suppression effect on the dynamic load of the gear transmission system is analyzed. Research results indicate that this control strategy has good control effects to suppress the dynamic load caused by a mutational external load, which confirms the effectiveness of the proposed control strategy

Electromechanical dynamic analysis for the cutting transmission system of the unmanned long-wall shearer under variable speed process

The drum shearer is one of the main equipments of the long-wall mining system. A typical condition to adjust the hauling and drum speeds is when the drum load exceeds the allowable value due to the hardness increase of the coal seam. Two schemes are utilized in this condition herein: (1) increasing the drum speed directly and maintaining the hauling speed; (2) decreasing the hauling speed firstly, then increasing the drum speed, finally increasing the hauling speed to the original value. The electromechanical dynamic model is firstly constructed for the Cutting Transmission System, and then the electromechanical dynamic analysis is conducted with both schemes, discovering that: the first scheme is quicker but may bring instability; the second is stable but slower; the resonance in frequencies obtained in different meshing conditions can be excited at the same time. At last, some advices are given for the development of the speed control strategies and mechanical design of the unmanned long-wall shearer

Resonance characteristics analysis of the power reflux hydraulic transmission system

The power reflux hydraulic transmission system (PRHTS), which is a new continuously variable transmission system, is put forward to enhance the efficiency of the torque converter. This study shows that the basic structure and operating principle of the PRHTS. Because the six-cylindered diesel engine’s operation range is between 40 Hz and 150 Hz, resonance point of the PRHTS should not exist in resonance region of engine. In order to study the resonance characteristics of the PRHTS, the dynamic model of the PRHTS is established by merging the planetary gear train dynamic model and torque converter dynamic model. This study also researches the amplitude-frequency characteristic curves of the PRHTS with different speed ratio and the effect of the torsional stiffness and damping coefficient to the amplitude-frequency characteristic of the PRHTS. The simulation result shows that the resonance frequency of the PRHTS could be excluded from engine’s operation range and the amplitude will decrease by changing the torsional stiffness and damping coefficient of the coupling

Influence of motor control characteristics on load sharing behavior of torque coupling gear set

The influence of the control characteristics of a direct torque control (DTC) motor on the load sharing behavior of a torque coupling gear set is studied by establishing a dynamic model of a multi-motor torque coupling system. The effects of run-out errors of the pinions of the torque coupling gear set on the powertrain are analyzed under steady operating conditions. The difference in rotational speed among the pinions becomes apparent, and the load sharing behavior deteriorates when there are run-out errors. The relationship between the control characteristics and load sharing behavior is studied. The difference in rotational speed decreases and the load sharing behavior improves as proportional and integral gains of the speed controller increase

Analytical coupling characterization of multi-stage planetary gear free vibration considering flexible structure

The mode characteristics and the parameter sensitivity for a two-stage NGW spur planetary gear system are studied based on the principles of structure natural dynamical characteristics. Considering the influence of flexible structure including shaft, the planet carrier, and the ring-gear, the coupled lateral-torsional-axial vibration dynamical model of the planetary gear system is established under the generalized coordinate system using the shafting element method. With the model, the natural frequency and vibration mode are solved, and the results indicate that the flexibility of ring-gear has a greater effect on natural frequency. Several distinct types of vibration mode are summarized, such as planet torsional mode, sun-gear shaft axial mode, ring-gear axial mode and so on. However, the translational mode which is one of the modes in the coupled lateral-torsional lumped mass model is not found in this study. Within the scope of the time-varying, mesh stiffness mainly affects the planet torsional mode of corresponding stage. Furthermore, the variation of radial bearing stiffness will also do effect on axial vibration mode, and the variation of bearing stiffness not only affects the vibration modes of adjacent stage of planetary gear train, but also affects the nonadjacent stage. The results demonstrate the coupling characteristics of the system under the free vibration condition

Load sharing characteristic analysis of short driving system in the long-wall shearer

The failure of the key parts, such as bearings and gears, in cutting drum long chain gear driving system of long-wall shearer is a crucial factor for service life of gear systems. A short driving system is driven by multiple electric motors for cutting drum has been proposed as an alternative to long chain gear driving system. An electromechanical dynamic model based on lumped-parameter method of short driving system is established considering the effect of intrinsic mechanical characteristic of electric motor. By taking into account time-varying stiffness, damping, electric motor synchronization error, manufacturing eccentric error and transmission error of gears, the load-sharing characteristic and dynamic characteristic of the multiple motor driving unit (MMDU) of short driving system are analyzed under shock load. The results of simulation show that the electric motor synchronization error has significant effect on the load-sharing characteristic of MMDU. The load-sharing coefficient evidently increases as the electric motor synchronization error go up, decreasing the electric motor synchronization error can improve the load-sharing characteristic of MMDU; and the synchronization error must be controlled fewer than 5 % to ensure the load-sharing coefficient of the MMDU under 1.1. The imbalance of dynamic meshing force distribution of pinions of the MMDU can be obviously decreased and the load-sharing characteristic of the MMDU can be greatly improved by controlling the synchronization error of electric motor, but the effect is unobvious by controlling the manufacturing eccentric error or transmission error. It provides an effective method to choose a suitable control ranges under different synchronization errors of electric motor according to different load-sharing requirements for the MMDU

Load sharing characteristic analysis of short driving system in the long-wall shearer

The failure of the key parts, such as bearings and gears, in cutting drum long chain gear driving system of long-wall shearer is a crucial factor for service life of gear systems. A short driving system is driven by multiple electric motors for cutting drum has been proposed as an alternative to long chain gear driving system. An electromechanical dynamic model based on lumped-parameter method of short driving system is established considering the effect of intrinsic mechanical characteristic of electric motor. By taking into account time-varying stiffness, damping, electric motor synchronization error, manufacturing eccentric error and transmission error of gears, the load-sharing characteristic and dynamic characteristic of the multiple motor driving unit (MMDU) of short driving system are analyzed under shock load. The results of simulation show that the electric motor synchronization error has significant effect on the load-sharing characteristic of MMDU. The load-sharing coefficient evidently increases as the electric motor synchronization error go up, decreasing the electric motor synchronization error can improve the load-sharing characteristic of MMDU; and the synchronization error must be controlled fewer than 5 % to ensure the load-sharing coefficient of the MMDU under 1.1. The imbalance of dynamic meshing force distribution of pinions of the MMDU can be obviously decreased and the load-sharing characteristic of the MMDU can be greatly improved by controlling the synchronization error of electric motor, but the effect is unobvious by controlling the manufacturing eccentric error or transmission error. It provides an effective method to choose a suitable control ranges under different synchronization errors of electric motor according to different load-sharing requirements for the MMDU

Load sharing characteristic analysis of short driving system in the long-wall shearer

The failure of the key parts, such as bearings and gears, in cutting drum long chain gear driving system of long-wall shearer is a crucial factor for service life of gear systems. A short driving system is driven by multiple electric motors for cutting drum has been proposed as an alternative to long chain gear driving system. An electromechanical dynamic model based on lumped-parameter method of short driving system is established considering the effect of intrinsic mechanical characteristic of electric motor. By taking into account time-varying stiffness, damping, electric motor synchronization error, manufacturing eccentric error and transmission error of gears, the load-sharing characteristic and dynamic characteristic of the multiple motor driving unit (MMDU) of short driving system are analyzed under shock load. The results of simulation show that the electric motor synchronization error has significant effect on the load-sharing characteristic of MMDU. The load-sharing coefficient evidently increases as the electric motor synchronization error go up, decreasing the electric motor synchronization error can improve the load-sharing characteristic of MMDU; and the synchronization error must be controlled fewer than 5 % to ensure the load-sharing coefficient of the MMDU under 1.1. The imbalance of dynamic meshing force distribution of pinions of the MMDU can be obviously decreased and the load-sharing characteristic of the MMDU can be greatly improved by controlling the synchronization error of electric motor, but the effect is unobvious by controlling the manufacturing eccentric error or transmission error. It provides an effective method to choose a suitable control ranges under different synchronization errors of electric motor according to different load-sharing requirements for the MMDU

Oral abstracts of the 21st International AIDS Conference 18-22 July 2016, Durban, South Africa

The rate at which HIV-1 infected individuals progress to AIDS is highly variable and impacted by T cell immunity. CD8 T cell inhibitory molecules are up-regulated in HIV-1 infection and associate with immune dysfunction. We evaluated participants (n=122) recruited to the SPARTAC randomised clinical trial to determine whether CD8 T cell exhaustion markers PD-1, Lag-3 and Tim-3 were associated with immune activation and disease progression.Expression of PD-1, Tim-3, Lag-3 and CD38 on CD8 T cells from the closest pre-therapy time-point to seroconversion was measured by flow cytometry, and correlated with surrogate markers of HIV-1 disease (HIV-1 plasma viral load (pVL) and CD4 T cell count) and the trial endpoint (time to CD4 count <350 cells/μl or initiation of antiretroviral therapy). To explore the functional significance of these markers, co-expression of Eomes, T-bet and CD39 was assessed.Expression of PD-1 on CD8 and CD38 CD8 T cells correlated with pVL and CD4 count at baseline, and predicted time to the trial endpoint. Lag-3 expression was associated with pVL but not CD4 count. For all exhaustion markers, expression of CD38 on CD8 T cells increased the strength of associations. In Cox models, progression to the trial endpoint was most marked for PD-1/CD38 co-expressing cells, with evidence for a stronger effect within 12 weeks from confirmed diagnosis of PHI. The effect of PD-1 and Lag-3 expression on CD8 T cells retained statistical significance in Cox proportional hazards models including antiretroviral therapy and CD4 count, but not pVL as co-variants.Expression of ‘exhaustion’ or ‘immune checkpoint’ markers in early HIV-1 infection is associated with clinical progression and is impacted by immune activation and the duration of infection. New markers to identify exhausted T cells and novel interventions to reverse exhaustion may inform the development of novel immunotherapeutic approaches