Soheil Zarkandi

Reducing consumed power of a robotic machine has an essential role in enhancing its energy efficiency and must be considered during its design process. This paper deals with dynamic modeling and power optimization of a four-degrees-of-freedom flight simulator machine. Simulator cabin of the machine has yaw, pitch, roll and heave motions produced by a 4RPSP+PS parallel manipulator (PM). Using the Euler–Lagrange method, a closed-form dynamic equation is derived for the 4RPSP+PS PM, and its power consumption is computed on the entire workspace. Then, a newly introduced optimization algorithm called multiobjective golden eagle optimizer is utilized to establish a Pareto front of optimal designs of the manipulator having a relatively larger workspace and lower power consumption. The results are verified through numerical examples.

A comprehensive dynamic modeling and actuator torque minimization of a new symmetrical three-degree-of-freedom (3-DOF) 3-PṞR spherical parallel manipulator (SPM) is presented. Three actuating systems, each of which composed of an electromotor, a gearbox and a double Rzeppa-type driveshaft, produce input torques of the manipulator. Kinematics of the 3-PṞR SPM was recently studied by the author (Zarkandi, Proc. Inst. Mech. Eng. Part C J. Mech. Eng. Sci. 2020, https://doi.org/10.1177%2F0954406220938806). In this paper, a closed-form dynamic equation of the manipulator is derived with the Newton–Euler approach. Then, an optimization problem with kinematic and dynamic constraints is presented to minimize torques of the actuators for implementing a given task. The results are also verified by the SimMechanics model of the manipulator.

The classical method to find possible solutions for path synthesis problem of planar mechanisms is continuation method. However, this method has some disadvantages such as producing unwanted extraneous and degenerate solutions and also producing mechanisms having defects. Moreover, many of the solutions are cognate of each other which can be obtained geometrically. Thus, finding the most feasible solution among all solutions is a cumbersome and time-consuming task. The main purpose of this paper is to explore applicability of heuristic algorithms to find multiple cognate- and defect-free solutions for path synthesis problems of planar four-bar and slider-crank mechanisms. To this aim, a new modified error function and an optimization-based algorithm is presented. The gravitational search algorithm (GSA) is utilized to minimize the modified error function. Efficiency of the method is proved through five case studies for path synthesis of four-bar and slider-crank mechanisms with and without prescribed timing.

This paper introduces a novel three degree-of-freedom spherical parallel manipulator with 3-PRR topology, where P and R denote a curved prismatic joint and a revolute joint, respectively. The first revolute joint of each PRR leg is actuated via a double Rzeppa-type driveshaft, and hence underlined. The manipulator has at most eight working modes and eight assembly modes. However, only one working mode and one assembly mode of the manipulator are acceptable during its motion which can be easily identified. Singularity and kinematic dexterity analyses reveal that the proposed 3-PRR spherical parallel manipulator has no forward kinematic singularity for a wide range of rotation of the moving platform around its central axis. An optimal design of the manipulator is also presented having a workspace with good kinematic dexterity.

In this article, a novel flight simulator manipulator with four degrees of freedom (DOFs) is introduced. The manipulator is called 4RPSP + PS parallel manipulator (PM) having a fixed platform, a planar moving platform, four active RPSP (revolute-prismatic-spherical-prismatic) legs and one passive PS leg. The first prismatic joints of RPSP legs are actuated and hence underlined. The passive PS leg constrains motion of the manipulator to three rotations and one translation (3R1T). The proposed 4RPSP + PS PM has closed-form solutions for both inverse and forward position kinematics through which unique working and assembly modes are found during motion. Singularity and kinematic dexterity analyses based on the Jacobian matrices reveal that the manipulator can be easily designed to have a workspace free of singularities. A constrained optimization problem is also presented based on the workspace and kinematic dexterity of the manipulator. Communicated by Ashitava Ghosal

Modelling and dynamic analysis of a novel four degrees of freedoms (DOFs) parallel manipulator (PM) with 4RSS+PS topology is conducted in this paper. The letters R, S and P denote revolute joint, spherical joint and prismatic joint, respectively, and underline denotes an actuated joint. The proposed manipulator has three rotational and one translational DOF (3R1T), while one of the rotational DOFs around the direction of translational DOF is free of limitation. In addition to the inverse kinematic, velocity and acceleration analyses, a computationally efficient scheme based on the principle of virtual work is presented to derive a closed-form dynamic equation of the 4RSS+PS PM. Then, the dynamic equation is applied for the inverse and forward dynamic analyses of the manipulator. Numerical examples are also studied with Matlab software and its SimMechanics toolbox to demonstrate correctness and efficiency of the presented dynamic modelling.

This paper deals with the second order kinematics of three degree-of-freedom (DOF) planar parallel manipulators. The simple and compact expressions are derived for both the inverse and forward acceleration analyses using screw theory. Moreover, as an example, a 3-DOF planar parallel manipulator is introduced and its kinematics is analyzed using the proposed method.