The proposed methodology for measuring of robotic arm positioning accuracy was verified on its construction consisting of three arms Arm I, II, III, while Arm I was manufactured by two different technologies AdM and CvM. A series of repeated measurements was performed for each robotic arm configuration with two different measurement methods CoM and NcM. The results of measurements were verified by statistical methods, based on which unsatisfactory values of measurements were excluded from the evaluation.
The use of proposed methodology is not only in the field of metrology and testing, but also to verify the interchangeability of components in construction of robotic systems. The methodology provides a detailed view of a dimensional chain quality of the robotic arm structure and determines conditions for maintaining accuracy during disassembly and reassembly of individual components of robotic system structures.
Statistical evaluation of the results verified that the obtained data was measured correctly and have a normal distribution.
For CoM with the same load of Arm I - AdM and Arm I - CvM:
homoscedasticity was confirmed for: CoM_0_Zz, CoM_1_Zz, CoM_2_Xx and CoM_2_Yy,
the conformity of the mean values has not been confirmed.
This means that for interchangeable Arm I it is necessary to modify the design of ArM I – AdM,
For NcM with the same load of Arm I - AdM and Arm I - CvM:
homoscedasticity was confirmed for: NcM_0_Y, NcM_1_Y, NcM_2_Y, NcM_0_Z, NcM_2_Z,
the conformity of the mean values for NcM_2_X has been confirmed.
This means that for mutually interchangeable Arm I - AdM, Arm I - CvM, to increase its rigidity, the structural design of the sensor holder must be modified.
Due to confirmed differences in positions for the same measured axis in different types of arms, we assume that Arm I - AdM, Arm I - CvM or an arm made by different technology may have dimensional deviations. From previous observations and calculations, for the research of other factors influencing the localization of the robotic arm position, these deviations in dimensions need to be eliminated.
Based on the results, we can conclude that production technology does not affect the positioning accuracy of the robotic arm, but the design of Arm I - AdM needs to be changed regardless of the operating load.
To further investigate, it will be appropriate to plan experimental measurements to better examine whether differences in a position of the robot arm are random or caused by loads or other factors that have not been taken into account (arm flexibility, load time, transport time, programmed trajectory of the robot arm...). The answer to the question will be known after analysis of accuracy of measured positions for Arm I - AdM and Arm I - CvM, depending on the measurement directions (X, Y, Z) and the load.
In the future, to increase the accuracy of measurement process, it will be necessary to use the proximity sensor MTN/EP080 Probe with higher sensitivity and increase rigidity of the proximity sensor holder. Furthermore, ensure the same position of the sensor holder for Arm I - AdM, Arm I - CvM on the robotic arm.