Meng Qingrui

A Fuzzy PID Cascade Control System of a Hydro-viscous Drive Speed Regulating Start

The effect of hydro-viscous drive speed regulating start depends both on reasonable structural design and appropriate control strategy. But the control system used at present cannot completely satisfy practical requirements. In order to resolve the problem, a fuzzy PID cascade control system is presented based on cascade control theory in this paper. In auxiliary control loop a PID controller is used to adjust the proportional relief valve, in main control loop a fuzzy PID controller is used to control the system. The fuzzy PID cascade control system was simulated by using Matlab software. The results show that the system can meet the actual demands quite well. To verify correctness of theoretical analysis, a test-bed of hydro-viscous drive speed regulating start was built and the experiments were carried out. The results prove the feasibility of the fuzzy PID cascade control system. Different from the simulation, in experiments, the output speed lags behind the given speed to a large extent because of the static friction force of the system. It is inevitable. More attention should be paid to this case in design of the control system.

Uneven distribution characteristics of contact force of large-sized non-asbestos brake pad

Large-sized non-asbestos brake pad is used in the brake system of mine hoister. During the braking process, uneven contact force distribution in the contact surface will occur, which accordingly leads to uneven wear and a shortened service life of the brake pad. To reveal contact force variation laws of large-sized brake pad during the braking process, using the software package ADINA, the braking process was simulated in this work. The results show that (1) the contact forces gradually present saddle-shaped distributions along the radial and tangent directions of the disk, and the temperature does not increase with the radius of the disk; (2) the contact forces increase with the nominal normal pressure, but not linearly, and nominal normal pressure should not be higher than 0.6 MPa when the initial speed is equal to 10 m/s; (3) both the contact forces and their increasing speed increase with the initial speed of the disk, but not linearly, and the initial speed should not be higher than 10 m/s when the nominal normal pressure is equal to 0.6 MPa. Correctness of the theoretical analysis was verified by brake experiments. Achievements of this work provide the theoretical basis for optimal design of the large-sized non-asbestos brake pad.