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Design and experimental analysis of mechanical force generators for performance improvement of machines

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2019
Ekinci, Mehmet Burak
Recently, a novel overconstrained mechanism with favorable dynamic properties, namely the MFG (Mechanical Force Generator), has been proposed. This mechanism can provide a desired mechanical force, or power variation depending on the position of its input links. This power profile can be adjusted in order to improve the performance of a machine and its actuators that are connected to the MFG. In previous works, determination of an optimum power profile for the MFG and determination of the MFG design parameters have already been studied. In this thesis, previously proposed methods are improved. New methods to determine optimum power profiles for MFG, which minimize the required maximum torque, maximum power output and energy consumption of the driving actuator, are proposed. In these methods, the motion of the machine is not changed and only the power and the torque output of the motors are taken as the optimization variables. A method for determining MFG power to obtain an MFG with open slot profile links, which are easy to manufacture, is proposed. The performances of the methods proposed in this study are assessed by applying them to a case study that has been considered in a previous work. It is observed that, for this case study, the performances of the proposed methods are better.vi In this thesis, the problem of determining the design parameters of MFG is also studied. It is pointed out that in order to generate an MFG power profile, MFG can be designed with either compression or tension springs. An improved algorithm which yields the design parameters of MFG is proposed. For the experimental verifications, a symmetrical slider-crank mechanism is used as a machine. A spring is placed between two sliders of the machine to simulate a conservative external load; and an appropriate MFG is designed for the aforementioned machine. An experimental setup is constructed to test the performance of the MFG. It has been shown via simulations and experiments that performance of a machine can be improved extensively by coupling a properly designed MFG to the machine.