This paper aims to explain the design of a novel time-varying sliding mode control of variable parameter (VP-TVSMC), which can effectively solve the anti-swing and positioning problem of distributed-mass double pendulum bridge crane system with its quick responsiveness and strong robustness to external interference. More specifically, this model initiates with the establishment of the dynamic equation of double pendulum crane model based on distributed-mass, then followed by the design of a time-varying parameter to realize the dynamic adjustment of the sliding mode surface and enhance the adjustment ability of the sliding mode surface, which is conducive to the global robustness of the double pendulum crane system under VP-TVSMC. With Lyapunov method and LaSalle’s invariance principle, the asymptotic stability of the system can be sufficiently proved. Finally, the adoption of three kinds of external interference signals and uncertain system parameters successfully verified the preeminent control performance and global robustness against external interference of the proposed controller. The simulation results indicate that compared with the conventional CSMC and PDSMC, the proposed control method can reduce the driving force of the trolley, ensure the rapid and precise positioning of the trolley, as well as restrain the load swing angle within 5° in an effective manner. In addition, compared with the symbolic function sgn( $S$ ), the designed continuous function th( $S$ ) possesses a better anti-chattering effect, thus strengthening of the control performance of VP-TVSMC.

This paper presents a novel tilt sensor using magnetic fluid, and the influence of the structural parameters on its detection performance is studied. This sensor comprises a core body and a shell. The core body as a sensing pendulum, which is composed of two permanent magnet rings and an iron core, is placed in the interior of the shell. The magnetic fluid, which produces the magnetic buoyancy and makes the core body suspension, is injected between the ends of the core body and the inner wall of the shell. There is a magnetic repulsion force between the permanent magnet rings placed at the ends of the shell and the core body, which provides an axial restoring force and makes the core body balance in the axial direction. When the sensor deviates from the horizontal position, the core body is displaced in the axial direction. The displacement reflects the tilt angle and can be measured by inductance coils wound on the shell. In our laboratory, a tilt sensor prototype was assembled, and some performance tests were carried out. The results show that its measurement sensitivity can reach 0.004° in the interval −10°–10°, and its detection performance can be further improved by adjusting the structural parameters. This sensor has the advantages of low cost, easy implementation, no-mechanical abrasion, and strong anti impact ability. It is flexible and can meet the different requirements of engineering applications.

Rolling bearings are widely used in rotating machinery. Their fault feature signals are often submerged in strong noise and are difficult to identify. This paper presents a new method of bearing fault diagnosis that combines the coupled Lorenz system and power spectrum technology. The process is achieved in the following three steps. First, a synchronization system based on the Lorenz system is constructed using the driving-response method. Second, when the tested signal is connected to the driving end, the synchronization error between the two sub-chaotic systems is obtained. Finally, the power spectrum density of the synchronization error is calculated and compared with the corresponding fault characteristic frequency. The coupled Lorenz system makes full use of the noise immunity and nonlinear amplification of the chaotic system. The detection characteristics and feasibility of the new method are verified by simulation and actual measured vibration data. The result shows that the noise reduction effect of the coupled Lorenz system is obvious. This method can improve the signal-to-noise ratio of the tested signal and provide a new way to perform fault diagnosis of rolling bearings.