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. Additionally, gearing for the input motor with a 1:7 ratio was added to ensure the motor would apply enough torque for the given additional friction. 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. A complete document containing all of the MATLAB code can be found within the Appendix section of this project page.
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