Comparison of various input shaping methods in rest-to-rest motion of the end-effecter of a rigid-flexible robotic system with large deformations capability

Motion control of flexible robots is one of the concerns of the researchers in the field of robotics. When the deflection of the flexible arms increases, considerable complexity is imposed in the problem. In the current study, for the first time, various approaches based on the frequency shaping method will be analyzed in motion control of the very flexible robot, in the point to point paths. To this end, a precise system modeling, based on the Absolute Nodal Coordinates (ANC) method, will be employed to the motion study of the system, containing the rigid and the very flexible parts. The provided formulation is very accurate and does not consider any simplifying assumption. As a result, it can exhibit the system behavior once the system undergoes large deformation and the resulted system is highly nonlinear. Comparing the obtained results with the previous conducted researches, the system modeling will be verified. Since the resulted nonlinear differential equations are highly stiff, some sophisticated numerical dynamics model methods, such as alpha technique, are utilized to numerical simulation of the system. Despite of the various advantages of the ANC modeling method, the controller designing is complicated based on this method. Therefore, the Input Shaping (IS) method are utilized to this end, in the current study. The IS method is based on the identification of the excited frequency modes of the system during the motion, and reduction of these frequencies energy in the resulted shaped inputs. The various shaping methods, such as Zero Vibration (ZV), Zero Vibration Derivative (ZVD), Extra Insensitivity (EI), and negative shaping method, will be utilized in the motion control of the very flexible link. The performance of the aforementioned methods will be evaluated using some criteria such as, time duration for the system transferring, the control effort, the robustness, and the steady state vibrations. Finally, the advantages/disadvantages of the mentioned methods will be discussed.