Hybrid controller with neural network PID/FOPID operations for two-link rigid robot manipulator based on the zebra optimization algorithm

The performance of the robotic manipulator is negatively impacted by outside disturbances and uncertain parameters. The system's variables are also highly coupled, complex, and nonlinear, indicating that it is a multi-input, multi-output system. Therefore, it is necessary to develop a controller that can control the variables in the system in order to handle these complications. This work proposes six control structures based on neural networks (NNs) with proportional integral derivative (PID) and fractional-order PID (FOPID) controllers to operate a 2-link rigid robot manipulator (2-LRRM) for trajectory tracking. These are named as set-point-weighted PID (W-PID), set-point weighted FOPID (W-FOPID), recurrent neural network (RNN)-like PID (RNNPID), RNN-like FOPID (RNN-FOPID), NN+PID, and NN+FOPID controllers. The zebra optimization algorithm (ZOA) was used to adjust the parameters of the proposed controllers while reducing the integral-time-square error (ITSE). A new objective function was proposed for tuning to generate controllers with minimal chattering in the control signal. After implementing the proposed controller designs, a comparative robustness study was conducted among these controllers by altering the initial conditions, disturbances, and model uncertainties. The simulation results demonstrate that the NN+FOPID controller has the best trajectory tracking performance with the minimum ITSE and best robustness against changes in the initial states, external disturbances, and parameter uncertainties compared to the other controllers.

Advanced Dynamics Processes Applied to an Articulated Robot

The paper presents the dynamics of a 2R planar articulated robot, developed by two original methods. One is the classical “Lagrangian” adapted by the author, and the second method is absolutely original. The dynamics of the robot are based in both cases on the variation of the inertial forces in the mechanism, or practically on the influence of the masses of the moving elements of the robot. The influence of external loads, weights and the load to be transported is also taken into account. Another original element of the work is the choice of speeds in such a way that they correspond to an optimum necessary for the inverse kinematics imposed on the robot. For this reason, the dynamic operation will be quiet and without large variations or vibrations. If the speeds of the two electric motors (preferably stepper motors) areadapted to those recommended by the author, the controller (PID) used will have a very light load. It is even possible to eliminate it if the adjustment of the two stepper motors (actuators) is performed according to the speeds indicated by the author of the paper. The kinematic motion imposed by the indicated optimal speeds is dynamically and successfully checked by both methods used.