Figure #3.1: Further crank design and hand calculations
After coming to a rough finalization of our crank arm design, basic calculations of the crank’s kinematic diagram showed that in order to open the bag, the force exerted on the bag by the L7L6 linkage needed to be twice of that required to pull the bag under normal conditions. In order to help increase the force of the L7L6 linkage, a rubber strip was applied to the inside of the wooden box’s hook mechanism in order to increase the friction between the hook and the bag, allowing for the crank to apply more force thanks to the associated friction helping pull one side of the bag in the opposite direction of the crank. After these hand calculations, we shifted our views to a virtual MATLAB simulation, where we performed the motion analysis for several significant parameters in the mechanism, mostly in regards to θ2, the angle of the motor gear.
Figure #3.2: Diagrams showcasing a counter-clockwise rotation of the machine, demonstrating how the mechanism pulls the slider bar backwards, in addition to defining many of the significant parameters used during the MATLAB analysis
Figure #3.3: Complete compilation of all MATLAB motion analysis graphs, featuring θ3, θp, d, b, ω3, ddot, and bdot as a function of θ2, in addition to the position of point P in relation to O2
Due to the nature of our machine having two degrees of freedom rather than simply just having one, the mechanism's full range linkage operation could not be rendered in a tool such as Planar Mechanism Kinematic Simulator. Instead, the linkage operation was animated within SolidWorks, as seen in the annotated video below:
Figure #3.4: Annotated animation of the full assembly as seen within SolidWorks (NOTE: Due to the large filesize of the video, the video may need to be downloaded to view.)