Colloquia

Samenvatting

Parallel manipulators are advantageous over serial manipulators regarding precision, speed and payload. Using flexure-based hinges as bearings at the joints of the manipulator further increases precision. This is due to the fact that flexure hinges evade the drawbacks of bearings such as friction, hysteresis and backlash. However, flexure hinges have the disadvantage of losing support stiffness when deflected. The disadvantage of losing support stiffness can be compensated by adding an additional link. This means that redundant actuation and redundant sensing are involved and that the speed and position measurement accuracy of the manipulator increase. The solution of redundant actuation and redundant sensing is not trivial.

This thesis is about the development of a redundantly actuated planar 3 degrees of freedom manipulator. The optimization of mechanical components is among others based on maximizing the out-of-plane stiffness. This is done in order to achieve a high parasitic eigenfrequency of the system which is beneficial regarding control. A dynamic model of the optimized manipulator is made for the analysis of the natural frequencies of the system. Furthermore, the dynamic model is used for simulation including a controller. The simulation is adjusted for controlling the experimental setup and an identification is carried out. The data of the identification is used for extracting characteristics of the system.

From the simulations it is shown that manoeuvring the end effector of the manipulator in the workspace region results in a change of characteristics regarding stress and eigenfrequency. The same applies for the experimental setup considering the eigenfrequencies. However, the simulated eigenfrequencies of the system differ in comparison with the eigenfrequencies of the experimental setup. One of the possible reasons is the effect of cogging of the motors which can be recognized as negative stiffness in the Bode diagram. Furthermore, misalignments that are introduced during the assembly of the manipulator can affect joint stiffness as well. In the end there is sufficient ground to gain regarding the verification of different mechanical properties.