Improving the strategies employed to control robotic arms is of great importance because of the increase in their use in advanced supervisory control strategies, such as digital twins. The inverse kinematic (IK) control of manipulators requires an IK solution and an awareness of the singular configurations. This work presents a complete IK calculation system with singularity analysis for the UR5 robotic arm created by Universal Robots. For a specific robot pose, different angle solution sets are obtained, and one of these solution sets has to be selected to achieve movement continuity and avoid singularities. Two methods for this double purpose are proposed: one calculates all the solution possibilities, and the other obtains only one solution set by following a sequence of decisions and calculations clearly stated by a finite state machine (FSM). Both methods are effective in managing singularities. The FSM-based method complements the IK solution procedure with advantages in the number of computations and performance by producing results that would not lead the joints to move abruptly. The results prove that the presented methods select an IK solution that does not result in a singular configuration, and that most of the time, they lead to the same valid IK solution.
Accurate motion control is required in mechatronic and robotic systems and is particularly important when the inverse kinematic control of robotic manipulators is done by controlling each joint independently; for this reason, it is necessary to find methods to optimize the position control strategies used in robotics, which can be achieved by focusing on controlling the speed of actuators. Controlled DC motors should be tested under extreme conditions for such applications. Performance indices pertaining to actuator wear-out and control accuracy are used for the evaluation. This study proposes a speed control strategy for a direct current motor that uses a model reference control (MRC) scheme and combines it with an internal model control (IMC) based proportional-integral (PI) controller. Three different controllers are used in the MRC to compare the performance of the proposed strategy with an IMC-based PID (Proportional Integral Derivative) controller in numerical simulations. For the experimental tests, particular tuning parameters are presented for the PID to control a DC motor when only a first-order model is identified. The proposed MRC-IMC scheme imposes a first-order response to the actuator while compensating for disturbances caused by load torque variations. Simulation and experimental results validate a better performance of the proposed control strategy.
Inverse kinematic control of industrial robotic manipulators is extensively used, for this reason it is necessary to improve current direct and inverse kinematic solutions. While some previous solutions present partial sets of equations and others have some inconsistencies, this study presents the complete derivation of an alternative set of equations for the inverse kinematic solution for Universal Robots robotic arms, particularly the UR5. The herein inverse kinematic solution is obtained by applying the conventional Denavit-Hartenberg algebraic method and is validated with the direct kinematic solution.
Understanding the roles of evening complex (EC) genes in the circadian clock of plants can inform how diurnal transcriptional loops in the clock gene network function to regulate key physiological and developmental events, including flowering transition. Gene regulatory interactions among soybean’s circadian clock and flowering genes were inferred using time-series RNA-seq data and the network inference algorithmic package CausNet. In this study, we seek to clarify the inferred regulatory interactions of the EC gene
GmELF3-1.
A gene expression analysis using soybean protoplasts as a transient model indicated regulatory roles of
GmELF3-1
in expression of selected flowering genes.
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