Design method and test research of D-knotter based on rigid-flexible contact dynamics

To achieve the flexible rope model with large deformation, macro modeling instruction based on ADAMS was used. A rope model is established for the virtual knot-tying test by using macro command. The motion simulation of rigid-flexible contact interaction between the rope and the actuators of D-knotter was accomplished under the environment of ADAMS. Firstly, D-knotter kinematical model of rope-holding, knot-winding and rope-biting, timing sequence of rope-holding, and position relation of rope-holding plate were established. Secondly, according to motion model in the simulation, a method of describing the effects of different φ and α accurately on D-knotter tying process was proposed. The φ is the timing difference between knotter hook and rope-holding plate, α is the intersection angle between the knotting hook shaft and the main shaft of knotter stand. Thirdly, the mechanical condition was created by adding tension to the rope model. This can graphically describe the rope status in the course of knot tying. Simulation results indicated that the value of α and φ were 90 degrees and 24 degrees respectively when rope was bitten accurately. Finally, the tying test of the physical prototype was built to validate the accuracy of theoretical model of rope-holding, knot-winding and rope-biting. Test results demonstrated that successful rates of knot-tying reached 100% without bundling straws and 99.25% with bundling wheat straws. The results indicated that the process of knot-tying could be demonstrated clearly under the environment of ADAMS.