# Experimental Investigation of Free-Motion Task Implementation on a Serial Metamorphic Manipulator
###### Abstract  
This paper presents an experimental investigation into the implementation of free-motion tasks on a serial metamorphic manipulator (SMM). Utilizing a previously established task-based optimization methodology, the dynamic performance of the SMM is evaluated through a combination of theoretical performance metrics and experimental data. The study aims to validate the SMM's ability to achieve optimized performance through structural reconfiguration. Theoretical models are compared against real-world free-motion task data, demonstrating strong correlations between analytical calculations and experimental outcomes. The discussion focuses on three key areas: the efficiency of joint controllers  
MRRs has thus become significant in a wide range of applications, from autonomous extraterrestrial missions [1] to wireless robotic arms for networked flexible manufacturing systems [2].  
Recent years have seen substantial research efforts dedicated to both the mechanical design and software integration of MRRs. Recent advancements in the mechanical design of MRRs have primarily focused on enhancing the modularity and robustness of these systems, leading to significantly enhanced reconfiguration efficiency, upgraded interconnection capabilities, and improved mechanical and electrical capacities of the modules [3; 4; 5; 6; 7; 8; 9]. On the software front, computational performance has been enhanced by aggregating the free computing resources of unused modules [10], and automated modeling procedures have been introduced to handle advanced genderless and multi-output connection ports, thereby reducing the time and effort required for reprogramming after reconfiguration, ensuring greater flexibility [11; 12]. The flexibility and adaptability of MRRs to varying task requirements have led to the development and implementation of numerous optimal task-based design methodologies. These approaches focus on tailoring the robot's configuration to specific operational objectives, enhancing performance while maintaining structural integrity [13; 14; 15].  
SMMs as a subclass of MRRs [16], employ a modular heterogeneous structure comprising active and passive modules. Active modules facilitate the robot's operations, while passive modules enable reconfiguration through manual offline operation. These modules adhere to strict interconnection rules within the serial chain and are developed to achieve a finite number of configurations. The topology changes induced by metamorphic structure synthesis and anatomy metamorphosis lead to a robotic system with modified kinematic and dynamic properties.  
Despite the significant advantages introduced by reconfiguration, numerous challenges emerge in the design, development, and operation of this category of robots. Reconfiguration introduces additional variables, that have a significant effect on the kinematic and dynamic characteristics and must be taken into account for accurate modeling, simulation, and control processes. Several methods have been proposed to address these challenges, including unified kinematics and dynamics models [17; 18; 19] and robust [20; 21] and adaptive control strategies [22; 23; 24]. Despite these advancements, it remains essential from an engineering point-of-view to be able to realize the effect of reconfiguration on overall performance and proceed to the validation of theoretical models and methods with actual experimental data to ensure accuracy and effectiveness.