Study on elevator vibration problem升降机振动问题研究
As an important overhead working machine, the vibration analysis of the elevator system has been widely concerned. In this paper, the vibration of the lift is analyzed, the system vibration mechanical model is established, the natural frequency of each stage of the system is obtained in different loads and different positions, the change trend of natural frequency of each stage with load and cargo position is analyzed, and the system response to the given initial conditions is determined. Elevator is an important vertical conveyor machinery, its cargo vibration and lift operation at the same time produced.
With the development of high-rise buildings, the lift speed is accelerated and the lift height is increased. This paper takes the rack and pinion elevator as the object, establishes the vibration mechanics model and vibration equation, and analyzes the response of the system to the given initial conditions by calculating the natural frequency of the system under different loads and different positions, providing reference for the vibration analysis of the elevator. Vibration model is established in this paper, vibration mechanics model in freight elevator, for example, by a pulley, the pulley frame, frame, steel wire rope, attached to the wall rack, guide rack, cargo, cab, the heavy, bottom cage and basis of the gear transmission device on the arrangement of the goods and arrange engages in guide rail on the shelf rack, make the goods make up and down along the guide rail, complete personnel and material transport, the actual structure as shown below. The structure features that the guide frame is mostly single, composed of standard sections, and the section form can be divided into rectangle and triangle. The guide rail is connected with the building by the wall bracket, and the rigidity is better. Cargo distribution is divided into two cages and a single cage, which generally balance the weight of the cargo and improve the balance of operation. The guide frame assembled by the standard joint has a large stiffness in the vertical direction. It can be considered that the pulley is installed on the rigid foundation, and the vibration mechanical model is established as shown. Physical meaning of each parameter in the vibration model: it is the rotating member in the cargo, load, steel wire rope and drive device. Since the natural vibration frequency of the system is only related to the mass and stiffness of the system, it is the natural frequency of the system in the characteristic equation rewritten as the vibration equation.
Since the elevator in operation is a system changing at any time, the parameters in the stiffness matrix are changing at any time, so the natural frequency of the system is changing at any time. According to the system parameters and software programming, the variation trend of natural frequencies of the aluminum alloy hoist under three working conditions of no-load, load-bearing and full-load is calculated. In the case of no-load, load-bearing and full-load, the change of natural frequency of the third order of the system has little influence, and its frequency curve basically coincides with each other. The maximum and minimum values of the first order natural frequency of the system (no load, load and full load) are located at the top and bottom of the cargo respectively; The maximum and minimum values of second order natural frequency are located at the position of 50m and top of the cargo when no load, at the position of bottom when load, and at the position of 60m and bottom when full load. The maximum and minimum values of the third order natural frequencies are at the bottom of the cargo. The results show that the natural frequency of the system is related to the load size and the change of the cargo position. High order natural frequency is greatly affected by the position of the cargo, but little affected by the load. Initial conditions at the time of the brake system response lifts in the process of work often start and brake, substitution to sum to the weight and wire rope combined respectively in the quality of heavy gear and rack tooth mesh composite stiffness and damping of stiffness and damping of wire rope pulley respectively respectively around the center of mass moment of inertia, the pulley rope and pulley wheel radius Angle displacement and velocity for the corresponding quality; As an incentive to act on goods. According to the vibration model, the vibration equation has 3 degrees of freedom. The coordinates are the position of each particle and the rotation Angle of the crown wheel.
The vibration equation is deduced as follows: the total dissipation energy of the total kinetic energy of the system is obtained from the equation. In order to understand the vibration characteristics of goods, to calculate the response of goods when braking, the free vibration of lift system under given initial conditions is solved. The response of the system to the initial condition is the mode of the main vibration of each order when t=0. When braking, the initial condition of the system is, and the system response to the initial condition is calculated. When the cargo is in different positions, the system has different responses to the initial conditions. When the cargo is near 40m, the system response does not change with the load, and the response under 40m is greater than that under full load, and the response under 40m is less than that under full load.
Conclusion: low order natural frequency is not sensitive to the position of the cargo. The minimum no-load first and second order natural frequencies do not change much with the change of cargo height. The higher natural frequency varies greatly with the change of the cargo position. The third natural frequency varies with the increase of the cargo height. The lower natural frequency decreases as the load increases, while the higher natural frequency is not affected by the load. The response of the system to the initial condition decreases with the increase of the height of the cargo when it is empty, increases with the increase of the height when it is full, and the response of the system to the initial condition is maximum when the fully loaded cargo is at the top of the lift.