A six-degree-of-freedom robotic manipulator inverse kinematics (IK) for position control is proposed for the bilateral teleoperation process that is implemented through a joystick for nuclear power plant dismantling operations. The control strategy of the manipulator includes the use of the joystick to generate the Cartesian space trajectory followed by the IK to yield the joint space trajectory for implementing position control. In this paper, a novel technique for the IK is proposed. It involves the use of the particle swarm optimization (PSO) algorithm with the inverse Jacobian (IJ). The special case of the dual PSO is based on dividing the PSO algorithm into two such that the trajectory position and orientation are separately optimized by the algorithms, resulting in a faster convergence. In contrast, the inverse Jacobian aids in generating a smooth joint trajectory. The integral sliding mode control (ISMC) is proposed for position control because it does not require information on system dynamics. The ISMC improves the system trajectory tracking performance by using a switching gain to compensate for system dynamics and perturbations (disturbance and unmatched uncertainties), ultimately reducing the time delay. The effectiveness of the PSO combined with the IJ and the robustness of the ISMC in the teleoperation process are confirmed by the experimental results.

Robot manipulators have complex dynamics and are affected by significant uncertainties and external disturbances (perturbations). Consequently, determining the exact mathematical model of a robot manipulator is a tedious task. Accordingly, accurate trajectory tracking is a dominant feature in the design of position control for robot manipulators. The main objective of this research is to design a robust and accurate position control for a robot manipulator despite the absence of an exact model. For this purpose, an extended state observer (ESO)-based sliding mode control (SMC) is proposed. The main concept in the ESO is to define and estimate the assumed perturbation, which includes known and unknown system dynamics, uncertainties, and external disturbances. Additionally, the ESO estimates the system states. This estimated perturbation information, which is combined with the SMC input, is utilized as a feedback term to compensate for the effect of the actual perturbation. The perturbation compensation improves the controller performance, resulting in a slight position error, less sensitivity to perturbation, and a small switching gain required for the SMC. The advantage of the proposed algorithm is that it only requires partial state information and position feedback. Thus, identifying the system parameters for the nominal model before designing the controller is unnecessary. The proposed algorithm is implemented and compared with the conventional SMC and the SMC with a sliding perturbation observer (SMCSPO) in a virtual environment based on MATLAB SimMechanics. The comparison results validate the robustness of the proposed technique in the presence of perturbation and show that the technique has a significantly reduced trajectory tracking error than the conventional SMC and SMCSPO.

In this study, a three-degree-of-freedom hydraulic system device configured as a master-and-slave manipulator system is considered. A methodology to estimate reaction force in aforementioned system is proposed without utilizing any force sensor/signal. A terminal sliding control with a sliding perturbation observer (TSMCSPO) is designed for coupled master-slave system. The fundamental benefit of the proposed scheme is that the sliding perturbation observer estimates the reaction force related to the end effector and second link without utilizing a force sensor. Robust and accurate position tracking is achieved with terminal sliding-mode control in addition to control of the slave manipulator. The position and force tracking for master-slave is estimated based upon bilateral control strategy. The difference in the reaction and operating force is included in the impedance model. The impedance model is implemented in the master device to provide the operator with a sense of the reaction force when it connects with the environment. The experimental results confirm the robust position and force tracking of the slave manipulator.

This research introduces a robust control design for multibody robot systems, incorporating sliding mode control (SMC) for robustness against uncertainties and disturbances. SMC achieves this through directing system states toward a predefined sliding surface for finite-time stability. However, the challenge arises in selecting controller parameters, specifically the switching gain, as it depends on the upper bounds of perturbations, including nonlinearities, uncertainties, and disturbances, impacting the system. Consequently, gain selection becomes challenging when system dynamics are unknown. To address this issue, an extended state observer (ESO) is integrated with SMC, resulting in SMCESO, which treats system dynamics and disturbances as perturbations and estimates them to compensate for their effects on the system response, ensuring robust performance. To further enhance system performance, deep deterministic policy gradient (DDPG) is employed to fine-tune SMCESO, utilizing both actual and estimated states as input states for the DDPG agent and reward selection. This training process enhances both tracking and estimation performance. Furthermore, the proposed method is compared with the optimal-PID, SMC, and $H_{\infty }$ in the presence of external disturbances and parameter variation. MATLAB/Simulink simulations confirm that overall, the SMCESO provides robust performance, especially with parameter variations, where other controllers struggle to converge the tracking error to zero.

In nuclear power plants (NPP), dismantling is the most technically involved process during their life time. During the dismantling process, public safety must be ensured. In crisis situations, a remotely controlled robot system is needed for the dismantling of NPP. Therefore, in this research, a bilateral tele-operation system is proposed to tackle these emergency conditions. Transparency can be improved by using force and position signal in the control strategy. In some applications, force cannot be determine directly using physical sensors. In this work, a novel tele-operated bilateral control strategy is proposed to estimate the reaction force of 3-degree-of-freedom (DOF) master and hydraulic slave manipulators without the use of a sensor. The control strategy is developed by using sliding mode control with sliding perturbation observer (SMCSPO). The sliding perturbation observer (SPO) estimates the reaction force at the end effector and second link without using sensors. The sliding mode control (SMC) is used as a tele-operated bilateral controller for the robust position tracking and control of the slave device. The impedance model is used to differentiate between the applied force (force exerted by operator) and the reaction force due to the remote environment. Different experiments were performed to verify the proposed strategy. The results indicate that the slave manipulator exactly follows the trajectory of the master device. A camera is used to take visual feedback of the workspace for safety purpose. This technique can also be applied for higher-order DOF manipulators in NPP.