0. Introduction

Hoist that gather equipment，electrical and hydraulic is a large scale equipment made up of mechanical and electrical systems，responsible for upgrading coal and gangue， lowering material，lifting personnel and equipment.Its safe and reliable operation directly affect the project can proceed smoothly and the staff life and property are safe.The reliability of the braking system is one out of an important factor in hoist system，brake clearance is an important factor for measuring reliability of the braking system，so accurately forecast brake clearance is particularly important.

1. Brake clearance analysis

In the work process hoist has axial channeling，brake disc runout and other phenomena，because of these factors the contact surface of break and brake disc from parallel to not parallel，so that the brake clearance become linearization，now the brake clearance mean maybe size up《Coal Mine Safety Regulations》，but the brake clearance max maybe pass the regulations，thus lead to the effective contact surface of break and brake disc decrescent，then brakingmoment shortage and lead to serious industrial accident.In order to conquer the problem the paper do a dynamic assessment for the brake clearance，and to predict the trend.

2. Dynamic assessment based on uncertainty unascertained theory

Hoist brake clearance size is affected on the axial channeling and brake disc runout，it is dynamic and has uncertainty unascertained information， so that it can be deal with unascertained theory.

Figure 1 is brake clearance measurement data curve，F(xiàn)igure 2 is a curve that use the evaluation model of this paper to deal with multiple sets of dynamic data，wherein the abscissa represents the sampling time， and the ordinate represents the measured value of the corresponding time brake clearance .

Uncertainty simulation curve

If the figure 2 in a stable state and not more than the upper limit of 0.6，then the proof brake clearance is in a normal state，otherwise prove brake clearance problematic，we need to stop the production timely and then to diagnose and repair hoist.

Compare with figure 1，figure 2 can predict the dynamic changes of uncertainty， understand the working condition of the hoist in advance，but figure 1 just is a real-time display of the hoist working condition.

3. Conclusion

（1）For predicting the dynamic changes of uncertainty，unascertained mathematics theory is use for modeling to brake clearance uncertainty in this method.With the measured data，it can improve equipment operation status and then runs in the optimum operating point，ensure its safe and reliable operation，imp

rove efficiency，extend equipment life.

（2）Between accuracy and complexity this method find a balance for dynamic analyzing and evaluating of uncertainty，provide a method practical， easy to implement and accurate.