Hydro-Québec’s research institute (IREQ) has developed since many years a robot with 6 degrees of freedom to achieve in situ hydropower equipments repairs. This robot was designed to perform multiple tasks as welding repairs, grinding or hammer peening, while the repaired equipment stays in place. This is why, the robot is very compact, portable and very light: all those characteristics involve vibrational issues such as the end-effector trajectory control and the material removal.
This thesis presents a numerical modeling of the SCOMPI robot with 6 degrees of freedom thanks to a multi-body software, MD Adams. Joints and links are defined as flexible in the model. Some phenomena such as non-linear stiffness, kinematic error and hysteresis are included into joints flexibility. Then, to consider the link’s flexibility, a finite-element software, Patran is used in the same time to determinate link’s modal information and introduce them into the Adams model. The vibrational behavior can be observed for a determined trajectory.
An experimental part is exposed. The objective is to validate the numerical model, by measuring the end-effector trajectory with a laser tracker. When performing data processing including the use of a minimization program with parameters, the data measured by the laser tracker can be compared with results simulated by Adams. The analysis of the dynamic measurements helps to determine the effect of different parameters such as stiffness, hysteresis and kinematic error. The importance of non-linear stiffness has been proved and the overall trajectory of the SCOMPI robot was found in agreement with the Adams model. The vibrational modes have also been determined with Adams software.
Finally, a simplified modeling of the grinding load is implemented in the numerical model by introducing an unbalanced rotating mass on the grinding wheel. This modeling is used to test the stability of the model but also to see vibrational oscillations when the robot is driven by a dynamic force at the end-effector.
| Date | 7 Oct 2013 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Zhaoheng Liu (Supervisor) |
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Santos, T. (Author),
Liu (Supervisor),
7 Oct 2013Student thesis: Master's thesis › Master in Engineering: Mechanical Engineering