Input shaping

Abstract: This paper presents wireless communicated real-time implementation of computed-torque control for a two-link SCARA robot and experimental works for two-dimensional input shaping control of a spherical pendulum. For comparison purpose, computed-torque control and individual joint control with proportional-plus-derivative logic are implemented for the tracking control of the SCARA robot. Moreover, wireless motion command transfer from a host PC (notebook PC) to the robot controller is implemented for user convenience. Second part of the paper presents experimental works for two-dimensional input shaping and tracking control of a spherical pendulum mounted at the end-effector of the SCARA robot. The logic of two dimensional input shaping is demonstrated through simulation and experimental works.

Abstract: This paper presents the vibration control problem of the single-link flexible composite manipulators. Two different materials of composite which are epoxy-glass and carbon-fiber are considered for both simulation and experimental analyses. Manipulators are obliged to perform a job such as pick and place applications and machining a workpiece. Therefore, a payload is attached to the manipulators. If the system is suitable for loading applications, the improved vibration control method is used to suppress the residual vibrations of the manipulators. The simulation results are verified with experimental results and it is observed that the proposed vibration control method significantly reduces the residual vibrations compared to passive vibration control method in literature. Additionally, the stresses during motion are analyzed for both simulation and experiment and the effectiveness of the proposed method on the stresses is investigated. Results showed that only the carbon-fiber manipulator is suitable for payload applications and its utilization efficiency can be greatly improved by the proposed method.

Abstract: In this paper, the equivalence between uniform B-splines of degree p and the output of a chain composed by p average filters is exploited for optimizing the trajectories used in robotic applications. In particular, the spline trajectories obtained with the proposed generator are characterized from a frequency point of view. Their frequency content is completely determined by the degree p and by the time period T between the equally-spaced knots. It is therefore possible to select these parameters with the purpose of suppressing residual vibrations, that may be present because elastic phenomena affecting the robotic system. In this sense, the proposed approach is very similar to input shaping methods and allows to find a trade-off between two different problems: on one side the requirement of exactly interpolating a set of given points by means of a complex trajectory such as a spline, on the other hand the need of suppressing mechanical vibrations. The effectiveness of the proposed approach is shown by applying it to the generation of a 3D trajectory for a cartesian robot with elastic joints.

Abstract: Transient air-fuel ratio control for lean burn engines is essential to achieve improved fuel economy and strict federal emission regulations. Unlike conventional Spark Ignition (SI) engines, lean burn engines are no longer operating in a narrow band around stoichiometric resulting in a very challenging air-fuel ratio tracking problem. An approach to combine an input shaping method together with Linear Parameter Varying (LPV) feedback control is proposed in this paper to solve the transient air-fuel ratio tracking problem. LPV air-fuel ratio control has been shown to regulate the air-fuel ratio at steady state engine operating conditions, reduce the variability of the closed-loop system, reject disturbance and guarantee robustness and stability in the presence of variable time delays. In this paper, an input shaping method is used to reduce the cost of feedback, and thereby enhance the air-fuel ratio tracking performance during engine transient operations. The prefilter is designed based on the closed-loop dynamics resulting from the LPV design. A systematic input shaping prefilter design process is developed. The designed prefilter successfully extends the closed-loop air-fuel ratio tracking bandwidth. Simulation results using Federal Test Procedure (FTP) drive cycle data are used to demonstrate the effectiveness of the input shaping prefilter. Moreover, the designed prefilter is structurally simple and computationally efficient.