Double Position Servo Synchronous Drive System Based on Cross-Coupling Integrated Feedforward Control for Broacher

Synchronization errors directly deteriorate the machining accuracy of metal parts and the existed method cannot keep high synchronization precision because of external disturbances. A new double position servo synchronous driving scheme based on semi-closed-loop cross- coupling integrated feedforward control is proposed. The scheme comprises a position error cross-coupling feedfor-ward control and a load torque identification with feed- forward control. A digital integrated simulation system for the dual servo synchronous drive system is established. Using a 20 t servo broacher, performance analysis of the scheme is conducted based on this simulation system and the simulation results show that systems with traditional parallel or single control have problems when the work- table works with an unbalanced load. However, the system with proposed scheme shows good synchronous perfor- mance and positional accuracy. Broaching tests are performed and the experimental results show that the maximum dual axis synchronization error of the system is only 8μm during acceleration and deceleration processes and the error between the actual running position and the given position is almost zero. A double position servo synchronous driving scheme is presented based on crosscoupled integrated feedforward compensation control, which can improve the synchronization precision.

Analysis and implementation of cross sync period underwater acoustical positioning techniques for underwater targets

The sampling rate of an underwater acoustical synchronous positioning system for the track of an underwater target will be decreasing during the process of positioning while the target moves away, resulting in the reduction of raw data and insufficient use of the processing ability of the positioning system. For a long time, this problem has remained unsolved, and it is even pushed forward recently because of the rapid development of modern electronic tech- niques. Based on the thorough study and investigation of the problem, we developed a new synchronous positioning technique called 'Cross Sync Period' underwater acoustical positioning. It can increase the sampling rate of an underwater acoustical positioning system for the track of an underwater target at long range significantly Besides, a new algorithm specially designed for the detection of the propagation time delay of the positioning signals called 'Mod-ulo Algorithm' was also developed, which makes the implementation of the 'cross sync period'underwater acoustical positioning technique easier and more efficient. These techniques have been successfully applied in a real positioning system. The system can position 5 underwater targets at the maximum range of 6 km simultaneously without any ambiguity of target distances with the working period of 0.4 s. The 'cross sync period' underwater acoustical positioning technique applied in the system was performed in lake and searun tests, and satisfactory re-sults were obtained.

siRNA screening of Rab GTPases reveal a role of Rab3b and Rab3c positive vesicles in cross presentation

Antigen cross-presentation in dendritic cells is a complex intracellular membrane transport process, but the underlying molecular mechanisms remain to be thoroughly investigated.

Pedestrian Crosswalk Overflow Violation in China:Characteristics and Countermeasure

The phenomenon that pedestrians do not walk in the crosswalk during pedestrian green is defined as overflow violation, which is illegal but common. Broadly varying crossing positions at far-side cross-section may result in widely distributed conflict points with left-turning and right-turning vehicles, which may cause the occurrence of severe conflicts. This paper proposes a model to estimate the overflow pedestrians' crossing positions at the far-side cross-section of signalized crosswalk, which enables us to better understand pedestrian overflow violation behavior and finally facilitate their safety. After analysis, the intersection geometry and destination are determined as the critical factors causing pedestrians to overflow. And then, Weibull distribution is employed to describe the stochastic characteristics of overflow pedestrians' crossing position distribution at the far-side cross-section. A crossing position distribution model which takes the crosswalk length, width and distance between crosswalk and destination into account is developed. The established model is validated by comparing the observed pedestrian crossing positions with the estimated crossing positions. The validation results suggest that the established model is capable of being adopted to estimate the overflow pedestrians' crossing positions at far-side cross-section. Based on the model, countermeasure for overflow violation can be put forward to prevent pedestrians from walking outside the crosswalk.