Some special specifics of dimensioning of a hydraulic cylinder as an executive device of an electrohydraulic actuator system

The hydraulic cylinder is dimensioned based on a static or dynamic criterion, assuming the desired operating pressure. The paper further analyzes the dimensioning of cylinders according to different load categories. The sizing of the hydraulic cylinder affects the choice of control algorithm parameters but also the stability of the system. How the cylinder dimension and the gain of the distributor affect the choice of the integral constant in the control algorithm in the case when we have the PI control law is especially considered. Then we have by definition an unsTable system 1 / s2 to which we provide stability through feedback.

Ensuring high-quality tightening of threaded connections according to dynamic criteria

The options of normalized tightening of threaded connections in the process of ultrasonic assembly according to the tightening the system’s response to the impact applied to the threaded connection during tightening are discussed. The original scheme of the device for monitoring the quality of tightening of a threaded connection by a dynamic criterion in the nonlinear domain is presented.

Optimization design of hydraulic performance in vaned mixed-flow pump

Vaned mixed-flow pump is widely used in industrial and agricultural cases. Considering mixed-flow impeller and space guide-vanes, the impeller and guide-vane blade angles need optimization design. In order to conduct optimization, the global dynamic-criterion algorithm with the ability of parallel running, dynamic criterion and escaping from local-best trap was used in this case. Based on numerical simulation and experimental verification, the 18 parameters' combination was optimized using this algorithm to achieve higher-efficiency in a specific flow rate range around the design condition. The numerical results showed that the weighted efficiency increased from 87.32% to 89.26% and the head coefficient decreased from 0.720 to 0.693. The improved efficiency and reduced head under design requirement helps to reduce the shaft power and energy consumption. The optimized blade inlet angle matches the inlet angle and improves the uniformity of flow in the impeller. The impeller outlet angle matches the guide vane inlet angle. Therefore, the flow regime becomes smoother in the rotor stator interaction region. The experimental results verify that the optimized pump efficiency was 85.75%. The measured head coefficient was 0.643 which meets the design requirement. This study provides a successful work for the green design of impeller and guide-vane of mixed-flow pump.

A Controller Avoiding Dynamic Model Degeneracy of Parallel Robots During Singularity Crossing

Parallel robots present singular configurations that divide the operational workspace into several aspects. It was proven that type 2 and leg passive joint twist system (LPJTS) singularities can be crossed with a trajectory respecting a given dynamic criterion. However, the practical implementation of a controller able to track such trajectories is up to now limited to restrictive cases of type 2 singularities crossing. Analyzing the structure of the inverse dynamic model, this paper proposes a global solution allowing the tracking of trajectories respecting the general criterion for any singularity that leads to potential issues of dynamic model degeneracy. The tracking is operated in the robot joint space. Experimental results on a five-bar mechanism showed the controller ability to successfully cross type 2 singularities.