Safety brake performance evaluation and optimization of hydraulic lifting systems in case of overspeed dropping

• The aim is to design safer hydraulic lifting systems in case of overspeed dropping.
• An energy indicator is defined to simply quantify the cushion performance.
• A multi-objective optimization method of hydraulic velocity fuses is proposed.
• The safety performance and the system efficiency are considered in the method.
• The proposed method has been successfully applied to a hydraulic elevator system.

Safety is the most important issue for mobile and industrial machinery, and overspeed dropping of lifting actuators is extremely hazardous to the equipment, environment and operators. In this paper, to evaluate and improve the safety brake performance of hydraulic lifting systems in this emergent case, a multi-objective optimization model was proposed. Considering the load impacts in the braking process, a novel indicator named remaining vibration energy was defined to simply quantify the cushion performance. A mathematical and simulation model was established, and then the simulation model was verified by experimental tests. Minimization of the remaining vibration energy, the brake distance and the pressure loss of the hydraulic fuse on normal working conditions were considered as optimization objectives after analysis of the system dynamic behavior. The optimization model using a genetic algorithm was applied to a heavy hydraulic elevator system. The results indicated that the pressure impact was reduced, and the plunger stopped more smoothly in the optimized system. Also the brake distance and the pressure loss of the fuse are limited by the design criterion. Therefore, this paper presents an optimization method of hydraulic fuses to design safer hydraulic lifting systems.