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Significance Statement
The complex geometry of the car bodies has made it necessary to continually improve the pretreatment process. Many conveyors have been developed and they can be divided into conventional conveyors includes overhead power and free conveyor, pendulum conveyor, auto-motor-hoist and modern conveyors including vario-shuttle and RoDip conveyor. The main drawback of conventional conveyors is the air pocket problem on the surface of car bodies. The drawback is overcome by modern conveyors characteristized by a conveyor technology that rotates the car bodies as they pass through the electrophoresis container. Moreover, vario-shuttle system and RoDip conveyor have shorter line, smaller container volume and less water. Although Vario-Shuttle and RoDip conveyor have been successfully applied in the automotive factories, they have some disadvantages: The cantilever beam is used in both conveyor systems. The load-carrying capacity of the conveyors is so low that they can only carry small cars for the pretreatment and electrocoating. In order to carry a heavy car, it is necessary to use two Vario-Shuttles. Furthermore, the Vario- Shuttle and RoDip conveyors, along with the car, are submerged in the liquid of the dipping process container. To protect the conveyor from corrosion and to isolate the electromagnetic field, the conveyor should be insulated and sealed.
Due to high stiffness of parallel mechanisms, conveyors with parallel mechanism have a high load-carrying capacity. In addition, the car body can be fixed on a hoisting frame so that the conveyor is not submerged in the liquid of the dipping process container and does not require insulation or sealing. Therefore, a conveyor utilizing parallel manipulators has great potential in paint shops. Furthermore, actuation redundancy can improve the dynamic load-carrying capacity of a conveyor. Therefore, conveyors with redundant parallel mechanisms have great potential in paint shop. In our work, a redundantly actuated parallel mechanism is proposed to develop a conveyor. The dynamic model is developed and the maximum dynamic load-carrying capacity is studied. The maximum dynamic load-carrying capacity of the redundant parallel conveyor is compared with that of its nonredundant counterpart. This work implies great potential of high performance conveyors for automobile industry, as well as extends the application of parallel mechanisms.
Journal Reference
Nonlinear Dynamics, October 2014, Volume 78, Issue 1, pp 241-250.
Jun Wu, Xiaolei Chen, Liping Wang, Xinjun Liu.
1. State Key Laboratory of Tribology and Institute of Manufacturing Engineering, Department of Mechanical Engineering, Tsinghua University, Beijing, 100084, China and
2. Beijing Key Lab of Precision/Ultra-precision Manufacturing Equipments and Control, Beijing, 100084, China
Abstract
Conveyors are important equipment in the painting shop. Conveyors with cantilever beams have low load-carrying capacity and can carry small cars. To solve this problem, this paper presents a novel conveyor that uses redundantly actuated parallel manipulators. A method is proposed to obtain the maximum dynamic load-carrying capacity of the conveyor by optimizing the internal forces of the redundantly actuated parallel manipulators. To improve the dynamic load-carrying capacity, approaches using counterweights are utilized and compared. Furthermore, the maximum dynamic load-carrying capacity of the redundant parallel manipulator is compared with that of its nonredundant counterpart.
