Parallel kinematics mechanisms (PKMs) represent a class of robotic systems comprising an end-effector and a fixed base interconnected by multiple independent kinematics chains. Compared to their serial kinematics mechanisms counterparts, PKMs offer inherent stiffness, agility, and pose accuracy advantages. Nonetheless, challenges such as singularities and limited workspace persist within PKM designs. This research project targets the enhancement of a machine tool utilizing linear motors, specifically a 3PRR planar PKM characterized by its restricted workspace and tilting capabilities. To overcome these limitations, the project introduces a modification in the topology and actuator placement, thereby augmenting the kinematics and dynamics performance of the system. The investigation primarily focuses on maximizing the machine's workspace and tilting range. Enhancing the overall capabilities of the parallel kinematics mechanism is the goal. The research methodology encompasses feasibility analyses, design optimization studies, workspace and orientation range assessments, stiffness analysis, and a finite element model presentation to evaluate the proposed enhancements comprehensively.

This work involved finding optimal PID gains for a nonlinear coupled mechanism. A parallel mechanism was presented as an example of such a mechanism. An accurate simulation that corresponds to the physical system was created, and friction parameters were identified through an optimization using a genetic algorithm. Subsequently, another optimization was performed to find optimal PID gains. Remarkable error reductions of 81% and 92% were observed in the experiments after implementing the optimal PID gains on the physical system, without any fine-tuning.

This paper presents a large-scale climbing robot that employs a parallel mechanism with three translational degrees of freedom as its locomotion method. Using a robot frame having a triangular pyramid shape, the robot provides a good stability during the locomotion and task execution. Three suction cups, called the perimeter cups, are attached to the vertices of the robot’s pyramid base, whereas three other suction cups called the middle cups, are attached to the end-effector of the parallel mechanism. The climbing motion is made by attaching and releasing the perimeter and middle cups one after another. The synchronization between the parallel mechanism’s motion and the suction cups during locomotion, as well as the improved gait trajectory, was established to ensure successful climbing. The control scheme of the robot integrates the servo control, the suction control, and the application control in a modular fashion. The successful climbing of the robot proves the scalability of the proposed climbing robot using active suction cups with an optimized design. Finally, a painting application was presented to demonstrate the robot’s capability to perform a wall painting task.

This paper analyzes the stresses, positional errors, and friction in lockable passive prismatic and revolute joints. The joints’ locking mechanisms that use solenoids to trigger the locking action have a self-alignment capability. The stress analysis evaluates the strength and material deformation of the joints’ components. The positional error analysis relates the clearances and contact deformations in the joints’ assembly with the positional errors of the joints. The friction analysis investigates how the friction during the locking motion interacts with the joint load, the pushing force, and the locking acceleration. The stress analysis was performed analytically for simplified cases and by finite element analysis for cases involving complex geometries and nonlinear contact. The positional error and friction analyses were performed analytically by deriving the kinematic and dynamic equations. Discussions based on the analyses provide a deeper understanding of the behavior of lockable joints that applies not only to the specific joints discussed in this paper but also to other lockable joints working with similar principles.