Kang, Chul-Goo (Konkuk University), Ha, Manh-Tuan (Konkuk University), Lee, Dong-chan (Konkuk University)
Two-Dimensional Input Shaping Control for Improved Tracking of a SCARA Robot with a Spherical Pendulum
Scheduled for presentation during the Poster session "Late Breaking Posters" (ThAP), Thursday, October 1, 2015,
09:45−10:00, Saal G1
2015 IEEE/RSJ International Conference on Intelligent Robots and Systems, Sept 28 - Oct 03, 2015, Congress Center Hamburg, Hamburg, Germany
This information is tentative and subject to change. Compiled on July 20, 2019
|Keywords Motion Control, Flexible Arms
I. INTRODUCTION Input shaping control is an effective method to suppress residual vibrations of a flexible robot [1-14]. However, it generally degrades temporal trajectory following (and, as a consequence, spatial trajectory following, too) due to the shaping of command input by convolving a sequence of impulses. Even though good tracking and residual vibration suppression are crucially important for flexible robot manipulators, e.g., large web handling robots or LCD handling robots, very little work has been done to design an effective controller to remove residual vibrations in multi-degree-of-freedom (DOF) motions and to minimize tracking errors together . In this work, we introduce a two-dimensional input shaper with a tracking aid which can remove residual vibration and can track a desired trajectory in a horizontal plane efficiently. As a test bed, we developed a two DOF SCARA robot, which can be controlled up to 0.1 ms sampling time wirelessly from a host PC. At the end-effector of the SCARA robot, a spherical pendulum is attached in order to generate two-dimensional flexible motion as shown in Figure 1.
II. TWO-D INPUT SHAPER WITH A TRACKING AID The spherical pendulum considered in this work moves in three-dimensional space with a string length constraint, and the support of it is attached to the end-effector of the two DOF SCARA robot. Thus the pendulum motion can be represented by using two variables of the bob and three variables of the support [16-20]. The control purpose is that the bob tracks exactly the support motion as fast as possible without residual vibrations. For this purpose, we have designed a two-dimensional input shaper by decomposing the support motion command into x and y directions and by applying decoupled component shapers in orthogonal directions. Furthermore, we have added a tracking aid to reduce the tracking errors, in which motion command and actual motion of the support are manipulated. The control performance of the two-dimensional input shaper with a tracking aid has been investigated through simulation and experimental studies.
III. RESULTS AND DISCUSSION The proposed logic is applied to rectilinear and curvilinear motion controls of the bob projected in a horizontal plane. Figure 2 shows simulation and experimental results when the proposed two-dimensional input shaper with a tracking aid is applied to a quarter-circle motion with trapezoidal velocity profile. In Figure 2, ‘Desired’ is trajectory command, ‘Without IS’ is actual trajectory of the bob when the support moves along a quarter circle, in which there exists big residual vibration, and ‘ZVDD IS’ is actual trajectory of the bob when the ZVDD (zero vibration, derivative, and derivative) shaper with a tracking aid is applied, in which residual vibration is almost removed. Figure 2 demonstrates the effectiveness of the two-dimensional input shaper with a tracking aid to reduce residual vibrations and tracking errors together.