Kinematic analysis and dimensional optimization of a 2R2T parallel manipulator

Abstract

The need of a device providing two translational (2T) and two rotational (2R) movements led us to the design a 3UPS-1RPU parallel manipulator. The manipulator consisted on a mobile platform connected to a base through four legs. That is, the manipulator layout has one central leg and three external legs at the same radial distance. By studying different locations of the legs anchoring point, we improved the first layout design, yet not the optimal one. On this basis, this paper focus on the optimal dimensional design of the manipulator. To this end, we put forward the kinematics equations of the manipulator in accordance to the anchoring points coordinates. Through a numerical approach, the equations enable to find the manipulator workspace. Also, we find a global manipulability index using a local dexterity measure. The latter index serves as optimal function. The optimization process considers joint constraints. Thus, we built a nonlinear optimization problem solved through sequential quadratic programming algorithms. We start by optimizing only a small set of parameters rather than the entire set, which gives us insights on the initial guess to optimize using the entire set. The optimal design layout varies from the original layout. Findings suggest that a task-oriented reconfiguration strategy can improve manipulator performance.

Performance Index for Dimensional Synthesis of Robots for Specific Tasks

“…Starting from the original design dimensions of the mechanism [25], we proceeded to perform the dimensional optimization using the IGCC as the objective function.…”

Optimal Reconfiguration of a Parallel Robot for Forward Singularities Avoidance in Rehabilitation Therapies. A Comparison via Different Optimization Methods

“…This paper deals with the motion of a PKM for human body lower extremity rehabilitation therapies. The methodology is based on previous works [22,24] but goes a step further in improving the reconfiguration of the robot by solving the optimization problem by different optimization procedures with the aim of avoiding getting trapped into a local minimum. These optimization procedures comprise evolutionary algorithms, heuristics optimizers, multistrategy algorithms, and gradient-based optimizers.…”

“…This paper is intended to provide insight into knee rehabilitation from the geometrical and kinematical redesign of a reconfigurable PKM (RPKM). The trajectories of the mobile platform that the RPKM must follow are established by the requirements of the patient's rehabilitation procedure and cannot be readily redesigned in advance for singularities avoidance [22][23][24]. The reconfiguration of the robot is posed as a nonlinear optimization problem subject to both linear and nonlinear constraints.…”

Stiffness analysis of a 3-DOF parallel mechanism for engineering special machining

“…Tian et al (2019) proposed a novel robot leg deformable parallel mechanism with the ability of reconstruction and motion change based on an innovative rotatable-axis revolute joint. Araujo-Gómez et al (2019) carried out kinematic analysis and size optimization of 2R2T (where R and T stand for rotational and translational degrees of freedom, respectively) parallel mechanism. Wu et al (2014) systematically introduced and discussed a series of 2-DOF parallel manipulators with equal-diameter spherical pure rotation.…”