Aspects concerning modeling of self-reconfigurable parallel robots

A reconfigurable robot is a robot that can change shape. Programming reconfigurable robots is complicated by the need to adapt the behavior of each of the individual module to the overall physical shape of the robot. In this position paper, we investigate a simple approach to allow the programmer to abstract over the concrete shape of a robot using the notion of a label as a simple means of addressing various parts of the structure of a robot. Labels provide the programming language designer with a means of stratifying two main components of a spatial programming language for modular robots, namely specifying the physical structure of a robot and specifying its behavior. Based on previous experience with the ATRON robot, we find that labels are a useful concept for programming modular robots.

A distributed operation health monitoring (OHM) method of modular and reconfigurable robot (MRR) is presented in this paper. The proposed method is shown to be able to monitor the health of each MRR joint module based on the deviation of the actuator output from what is commanded. Driven by the desire of avoiding the need of joint acceleration measurement, a novel health indicator that reflects the operation health of an MRR module is developed by filtering the commanded joint torque generated by the joint controller and comparing it with a filtered torque estimate derived from the dynamic model of MRR. The proposed approach can work effectively for MRR modules in any working mode, including stationary state. The proposed scheme has been evaluated experimentally, and the results demonstrate its efficacy.

Modular robots are robots built from multiple modules which can reconfigure the shape of the whole robot. This makes them a promising technology to realize highly adaptable and re-configurable robots. One of the main challenges in modular robotics is to detect and heal the system from a state of partial or complete disconnection. Partial disconnection can be achieved by removing the links between the modules. Complete disconnection can be achieved by removing all the connections between two group of modules. It is important for the modular robots to detect a failure between connections since the mobility and the functionality of the robot depend on it. This paper presents a novel approach to detect disconnections in lattice based modular robots. It detects the disconnections using a hierarchical algorithm. The leader of the system constructs a spanning tree, assigns a coordinate to each module and compares it to detect the disconnections. The simulations shows the ability to detect all partial disconnections. Furthermore, the complexity regarding the number of messages sent is linear against the number of modules in the system.

Compared with the fixed morphological robots, the self-reconfigurable robots (SR) are very flexible as they can adapt to a wide range of task requirements. However, the current efforts on SR mainly focus on the locomotion issues, while the manipulation capabilities of existing systems are still quite limited. In this paper, a new kind of mobility reconfigurable robotic structures (MRRS) with self-reconfiguration ability is presented. The reconfigurable topology and variable mobility characteristics of the MRRS are realized by integrating the cooperative kinematic mechanism (CKM) and the separable parallel kinematic mechanism (SPKM) into one robotic system, which makes the robot capable of reconfiguring its mechanical assembly to adapt to the multiple motion task requirements. Based on Lie group of displacements, the commonly used robotic tasks are first classified into three categories: positioning motion, tooling motion and grasping motion, possible motion types of these tasks are enumerated, then how to deal with the multiple tasks by using the MRRS is synthesized systematically. Finally, a multi-task working process is employed as an example to illustrate the advantages of this reconfigurable robotic structure.

Self-reconfigurable robot is a kind of robot that is able to recover its original function after partial damage of the robotic system. This is achieved by making changes on the partially damaged robot. This paper put forward a kind of self-reconfigurable quadruped robot based on the resilient theory. First, the concept of the self-reconfigurable robot and the recovery strategy were introduced. Secondly, a novel architecture of modular quadruped robot made by LEGO material was proposed. The connector of interfaces was taken into consideration. At last, the overall mode of the motion and control method with the help of NXT G program were proposed. The analysis of the overall gait ensures the stability of motion in this phase. As for the uncertain environmental damage to the robot, the robot is able to repair itself by changing the movement type automatically to ensure it continues to work. The result shows that the quadruped robot meets the requirements of resilience and self-reconfiguration.

The paper proposes a novel approach to the objects localization in the working area of a modular reconfigurable robot (MRR), which implies the installation of stationary monitoring points (SMP), consisting of detachable robot’s modules and in- stalled by robot itself. This approach is based on the architecture of the MRR control system previously proposed by the authors and a new method for comparing information about the speed and position obtained from various sensors. The key steps of the approach are following. Upon arriving in the target area, the MRR places SMPs, which consist of a power source, a computing device, a wireless transceiver and a sensor, detached from the robot. Then SMPs monitor the working area using different types of sensors (cameras, rangefinders, etc.), perform segmentation of the measured data and transfer this information to the robot. Further a sensor fusion is performed using a novel object tracking method, which makes it possible to localize target objects even in those cases when they are not visible by some of the SMPs. One of the key advantages of the new approach is a possibility of implementation in the distributed architecture of a MRR. The simulation results show that proposed method has Multiple Object Tracking Accuracy (MOTA) metric of 86 %, which is higher than the most of its analogues, while the estimated dynamic object localization error in a 8x7 m working area using 2 cameras and 1 rangefinder does not exceed 10 cm.

SUMMARYThe fields of modular reconfigurable robotics and programmable matter study how to compose functionally useful systems from configurations of modules. In addition to the external shape of a module configuration, the internal arrangement of modules and bonds between them can greatly impact functionally relevant mechanical properties such as load bearing ability. A fast method to evaluate the mechanical property aids the search for an arrangement of modules achieving a desired mechanical property as the space of possible configurations grows combinatorially. We present a fast approximate method where the bonds between modules are represented with stiffness matrices that are general enough to represent a wide variety of systems and follows the natural modular decomposition of the system. The method includes nonlinear modeling such as anisotropic bonds and properties that vary as components flex. We show that the arrangement of two types of bonds within a programmable matter systems enables programming the apparent elasticity of the structure. We also present a method to experimentally determine the stiffness matrix for chain style reconfigurable robots. The efficacy of applying the method is demonstrated on the CKBot modular robot and two programmable matter systems: the Rubik's snake folding chain toy and a right angle tetrahedron chain called RATChET7mm. By allowing the design space to be rapidly explored we open the door to optimizing modular structures for desired mechanical properties such as enhanced load bearing and robustness.

The last few years have witnessed an increasing interest in modular reconfigurable robotics for education, inspired robotic research, and space applications. This paper presents the latest results of the Cube-M modular project. Firstly, an overview of the research achievements in modular robot is given. Then the new modular robot Cube-M with one degree of freedom, an improved version of the Y1 modular robot, is presented. After that, the discussion focuses on the realization of a distributed hardware and control. Each module has embedded intelligent capabilities with an independent onboard controller to enable the realization of completely modular design. In the end, a snake-like robot prototype is built to confirm the feasibility of our design principle.

With the development of the micro-electronics and computer technology, especially with the expansion of field programmable gate array (FPGA), the reconfigurable system technology is becoming the key issue of research and application. In this paper, the principle of the dynamically reconfigurable FPGA, the method and flow of the configurable design are introduced. Based on the application requirement of the modular reconfigurable robot (MRR), a designing method of reconfigurable robot controller is proposed, which is based on the Advanced RISC Machine (ARM) processor and FPGA. The design principle, internal logic function design and the design course of the reconfiguration method are presented. Finally, the experiments of the MRR prove the feasibility of the reconfigurable robot controller to different configuration requirement of MRR and the efficiency of the software and hardware resource.

A conceptual framework and optimization for a task-based modular harvesting manipulator

The concept of reconfigurability and its applications in robotics have become prominent in the past few years as they provide versatility, adaptability and scalability to the systems. The reconfigurable robots can perform tasks in outer space, under the sea and in hazardous environments by rearranging their physical configurations to alter the system’s behavior and geometry. However, the concept of reconfigurable robots is not just constrained by the mechanical reconfiguration of the components, for the system should also demonstrate a modular reconfigurable behavior to newly imposed conditions. The objective of this work was to design and implement a multi-modal reconfigurable platform based on the concept of “form follows function” to be integrated with 3D-Immersive telepresence systems. The developed system was analyzed to verify the feasibility and functionality of the proposed architecture, and suggestions were made for future improvements.

This paper presents a novel 6-URS self-reconfigurable all-dimensional walking robot. The model of the 6-URS self-reconfigurable walking robot is established, then its reconfiguration modes are proposed. Based on the screw theory, the degrees of freedom (DOF) of this robot before and after reconfiguration are analysed separately to verify the feasibility of self-reconfiguration. This robot can achieve self-reconfigurable function with the design of self-reconfigurable limbs. Moreover, the trajectory planning and simulation of three kinds of gaits are performed, including walking horizontally, turning and climbing. The above analysis shows that the 6-URS self-reconfigurable all-dimensional robot satisfies the walking requirements and has the reconfigurable ability in unstrcutured environment.

Currently available industrial robots are mainly of monolithic structure. Hence, the geometrical dimensions and the configuration of robotic arms are immutable. A modular design of serial manipulators allows to vary the structure of serial kinematic chains, for example, to adapt the system to a specific handling task. In this work we present the concept of a modular robot which has general kinematic structure by means of curved link elements. We show how to describe intuitively the assemblage of modular manipulators with curved links (referred to as Cuma-arms) by a parameter set. A Cuma-type arm and a dedicated path which can be followed by the end effector with 16 different postures is presented. For computation of the inverse kinematics of general serial 6R manipulators the algorithm of Husty and Pfurner is used and implemented on a real system.

This chapter studies the dynamic issues of modular robots. Since a modular robot has unfixed configurations, it is very difficult to derive the closed-form dynamic model manually. Following the geometric modeling approach, a dynamic formulation scheme is introduced, which can generate both the recursive and the closed-form dynamic models of a tree-structured modular robot from a given Assembly Incidence Matrix (AIM) automatically.

Self-reconfigurable robots present advanced solutions for various automation applications in domains, e.g., planetary exploration, rescue missions, cleaning, and maintenance. These robots have the ability to change their morphology according to given requirements or adapt to new circumstances, which, for example, can overcome constraints while navigating within a working environment. However, the autonomous navigation of self-reconfigurable robots is more complex than that of robots with fixed shape because of the intrinsic complexity of robot motions, especially in complicated obstacle environments. To address this challenge, we present a novel path planning method for reconfigurable robots in this study. The technique is inspired by the similarity between a robot motion path and a heat conduction path at the steady-state. In the heat transfer analysis domain, feasible moving locations are modeled as materials with high conductivity, while obstacles are considered thermal insulators, and the initial and destination positions are assigned as heat sink and heat source, respectively. The temperature profile and gradient calculated by finite element analysis are used to indicate the possible moving directions from the heat sink to the heat source. Based on the temperature gradient ascent, a step-wise conductivity reaching algorithm is developed to optimize robot paths using customized multi-objective functions that take the costs of morphology changes, path smoothness, and safety into account. The proposed path planning method is successfully applied to the hinged-tetro self-reconfigurable robot and demonstrated on several virtual environments and a real-world testbed environment.