Modular Reconfigurable Robot Research Articles

Decoding modular reconfigurable robots: A survey on mechanisms and design

The intrinsic modularity and reconfigurability of modular reconfigurable robot (MRR) systems confer advantages such as versatility, fault tolerance, and economic efficacy, thereby showcasing considerable potential across diverse applications. The continuous evolution of the technology landscape and the emergence of diverse conceptual designs have generated multiple MRR categories, each described by its respective morphology or capability characteristics, leading to some ambiguity in the taxonomy. This paper conducts a comprehensive survey covering a wide range of mechanism and design aspects of MRR systems, spanning from 1985 to 2023. It introduces an innovative, unified conceptual framework for understanding MRR hardware, which encompasses three pivotal elements: connectors, actuators, and homogeneity. Through the utilization of this trilateral framework, this paper systematically interprets and classifies MRR systems over the years, aiming to provide a structured taxonomy perspective and enhance understanding of MRR. It explains the fundamental attributes characterizing MRR systems and their compositional aspects, providing insights into their design, technology, functionality, and categorization. Augmented by the proposed trilateral framework, this paper also elaborates on the trajectory of evolution, prevailing trends, principal challenges, and potential prospects within the field of MRR.

Gait coordination control of bipedal modular reconfigurable robot based on adaptive neural network

This paper proposed an adaptive neural network (NN) control method to track the desired trajectory of a bipedal modular reconfigurable robot (MRR), which can solve the gait coordination problem of bipedal MRR. The leg dynamic model and the body dynamic model of bipedal MRR are established based on the Newton–Euler iterative method, and the global dynamic model is subsequently established. Aiming at the gait coordination problem between double support phase (DSP) and single support phase (SSP), the desired trajectory is generated based on the zero-moment point (ZMP) method. The adaptive NN controller is designed to track the generated desired trajectory, which also compensates interconnected dynamic coupling (IDC) effects of the bipedal MRR. The stability of bipedal MRR system is proved by Lyapunov theory. In the end, the effectiveness of the control method is verified by comparative simulation. The simulation results show that the proposed adaptive NN method reduces the position tracking error by [Formula: see text] and the control torque by [Formula: see text] compared with the existing control methods.

Miniature Modular Reconfigurable Underwater Robot Based on Synthetic Jet.

Modular reconfigurable robots exhibit prominent advantages in the reconnaissance and exploration tasks within unstructured environments for their characteristics of high adaptability and high robustness. However, due to the limitations in locomotion mechanism and integration requirements, the modular design of miniature robots in the aquatic environment encounters significant challenges. Here, a modular strategy based on the synthetic jet principle is proposed, and a modular reconfigurable robot system is developed. Specialized bottom and side jet actuators are designed with vibration motors as excitation sources, and a motion module is developed incorporating the jet actuators to realize three-dimensional agile motion. Its linear, rotational, and ascending motion speeds reach 70.7mms-1, 3.3rads-1, and 28.7mms-1, respectively. The module integrates the power supply, communication, and control system with a small size of 48mm × 38mm × 38mm, which ensures a wireless controllable motion. Then, various configurations of the multi-module robot system are established with corresponding motion schemes, and the experiments with replaceable intermediate modules are further conducted to verify the transportation and image-capturing functions. This work demonstrates the effectiveness of synthetic jet propulsion for aquatic modular reconfigurable robot systems, and it exhibits profound potential in future underwater applications.

Simulated vs Actual Application of Symbiotic Model on Six Wheel Modular Multi-Agent System for Linear Traversal Mission

Constant demand for sustainable mechanisms to perform heavy and risky tasks has driven more robotics innovations to arise. Modular reconfigurable robotics system is one of these promising technologies that are continuously explored. Homogeneous types, to be specific, can accomplish similar missions at the same time as individual and heavier missions as an integrated system. This paper presents an analysis of the carrying capacity of a six-wheeled modular multi-agent system using the symbiotic model. The objective is to determine the resulting symbiotic relationship of a given configuration and module state combinations. The results show that the dominant relationship among the trials for linear traversal mission is commensalism. That means, the system neither benefits nor gets harmed from the symbiosis formed. This is true both in simulated and actual test environments although the percentage difference is about 12%. MATLAB Simulink was used for simulation while Maqueen robot in a 3D-printed chassis was used for actual testing. With this study, future configurations for several other missions such as object tracking and ramp climbing can be assessed using the same approach so that possible fault occurrence during operations can be prevented since the developed analysis method is performed prior to the deployment of the system.

Bidirectional Polytope Trees to Optimal Formation Path Planning for Reconfigurable Modular Robots

Bidirectional Polytope Trees to Optimal Formation Path Planning for Reconfigurable Modular Robots

Mathematical modeling method based on heterogeneous cellular network algorithm and computer multi-dimensional space

Due to the rapid development of services such as computer multi-dimensional space, traditional cellular networks are quantified and diversified, and it is difficult to meet the future connection needs of green network users. The heterogeneous cellular network algorithm places multiple microcells and relay nodes under the macrocell. This multi-layer network architecture can not only shorten the data transmission link, but also reduce the energy consumption of base stations and terminals. In addition, through spectrum space reuse Capability and spectrum efficiency improve the efficiency of the system, but this also increases the number of base stations and network construction costs, and significantly increases energy consumption and operating costs of operators' electricity expenditures. In addition, in order to achieve parallel transmission of data, placing multiple millimeter wave input and output antenna systems in heterogeneous network microcells can meet the high-speed data needs of indoor users, but the antenna array requires many RF links to drive, which increases the hardware implementation. Complexity, cost and energy consumption. According to the above-mentioned problems, a reconfigurable modular robot is established based on the multi-dimensional computer space. It is composed of modules with the same interface and can be assembled into different configurations according to different tasks. Compared with the original robot, the reconfigurable modular robot is more adaptable to the work and environment, and flexible. Then the basic and core technologies such as kinematics, type synthesis, scale synthesis, error and control of the reconfigurable modular robot are mathematically modeled, so as to effectively apply and promote the reconfigurable modular robot in practice, and make it has theoretical and practical value.

An automatic modeling method for modular reconfigurable robots based on model identification

An automatic modeling method for modular reconfigurable robots based on model identification

Configuration Enumeration of Multi-Limb Reconfigurable Modular Robots

By introducing modular and reconfigurable designs, the Multi-limb Reconfigurable Modular Robots (MLRMR) have many different configurations instead of a single fixed configuration, which greatly expands the boundaries of the operation. However, the number of non-isomorphic configurations increases exponentially with the number of modules, making it necessary to explore the enumeration method theoretically. Based on the group theory, the permutation groups of the Multi-limb (including three-limb, four-limb, and five-limb) Reconfigurable Modular Robots are established in this paper, and the theoretical formulas of configuration enumeration are derived by applying the Pólya enumeration theorem. This work can be used as the basis of configuration analysis.

Configuration selection for tip-over stability of a modular reconfigurable mobile manipulator under various application situations

AbstractA method is presented for configuration selection to obtain the best tip-over stability of a modular reconfigurable mobile manipulator (MRMM) under various application situations. The said MRMM consists of a modular reconfigurable robot (MRR) mounted on a mobile platform. The MRR in different configurations creates different wrenches onto the mobile platform, leading to different tip-over moments of the MRMM, even though the joint speeds or tip speeds remain the same. The underlying problem pertains to selecting one configuration of MRR for reconfiguration that would obtain the best tip-over stability under a given application. First, all the permissible configurations are identified through an enumeration method. Then, the feasible configurations are determined based on application-oriented workspace classifications. At last, two workspace indices, vertical reach and horizontal reach, are used to select an optimal configuration. The tip-over stability analysis and evaluation of MRMM are carried out for verification for three cases including vertical, horizontal, and general 3D space applications. The results demonstrate the effectiveness of the proposed method.

Adaptive dynamic event-triggered control for constrained modular reconfigurable robot

Compared with traditional robot, modular reconfigurable robot (MRR) has the advantages of strong environmental adaptability and flexible task completion. According to the optimal tracking control problem (OTCP) of MRR under some restricted conditions, this paper puts forward a constrained dynamic event-triggered control (DETC) for MRR system with disturbance through adaptive dynamic programming (ADP), which can minimize the information interaction quantity under the premise of system stability and expected control effect. In view of the uncertainty of model coupling part, the identification network is used to estimate the dynamics of MRR and the estimation error is proved to be uniformly ultimate bounded (UUB). The other three groups of critic, action and disturbance neural networks (NNs) are established by the approximation principle of ADP. The optimal control pair is obtained through policy iteration (PI) with DETC, and the triggering condition is designed based on the asymptotic stability of MRR system. At last, the strengths of the algorithm in this paper are validated through simulation experiments.

Autonomous distributed system for single-legged modular robots to traverse environments by adaptive reconfiguration

Reconfigurable modular robots have the potential to achieve a range of tasks by changing their physical configuration. To identify a suitable configuration, the use of libraries has been suggested. However, such libraries usually assume centralized control, and developing a hardware-dependent library for all assumed tasks may be impractical. In this article, we focus on slope and gap traversal tasks for single-legged reconfigurable modular robots. We propose an autonomous distributed system to traverse the environments without determining the desired configuration a priori. Each module locally monitors the failure risk of the environment traversal for the entire robot. When it detects the high failure risk, the entire robot changes its morphology by adding an additional module to the component of the robot at a connecting place determined by the failure experience. By repeating the procedure, the entire robot gradually adapts the morphology to the environment and finally traverses the environment. Through dynamic simulations and robot experiments, we validated that entire robots with several initial configurations succeeded in changing their morphologies and traversing several slope and gap environments.

Magnetically Controlled Modular Cubes With Reconfigurable Self-Assembly and Disassembly

Reconfigurable modular robots, which can actively assemble and disassemble on command, offer the possibility of mesoscale (milliscale and microscale) manufacturing with robustness and controllability. In this study, we present a design of a scalable modular subunit with embedded permanent magnets in a 3-D printed cubic body. The subunit can be wirelessly controlled by an external uniform magnetic field. We also present controlled assembly–disassembly techniques for these subunits. Our modular robotic platform is highly reconfigurable and can create programmable, predetermined patterns based on open-loop control. The 2-D motion planner computes all reachable polyomino shapes from an arbitrary initial configuration and provides the shortest movement sequences to form each shape. Experimental results match computational modeling, demonstrating robust and reproducible behavior of the modular robotic platform that is promising for mesoscale manufacturing applications. Two cube sizes were tested: 10-mm edge lengths and 2.8-mm edge lengths.

Enumerating the Nonisomorphic Configurations of a Modular Reconfigurable Robot

Abstract By introducing the modular and reconfigurable design, the limbs of a hexapod robot can be assembled into different configurations to meet various task requirements. Contrary to the fixed configuration system, the task capabilities of the modular reconfigurable robot vary with the configurations. This article addresses the problem of the configuration enumeration and configuration expression of a modular reconfigurable robot. First, by establishing the permutation group of the regular hexagon (the base shape of the modular reconfigurable robot) and adopting the Pólya enumeration theorem, the theoretical formula of the nonisomorphic configuration enumeration is derived. Then, considering the change in structural features, equivalence relations based on structural features are defined and the structural feature method (SFM) is proposed to enumerate the nonisomorphic configurations. In addition, to express configurations more intuitively, a senary vertex identification array with the same dimension as the number of modules is presented, which can be transformed from the decimal index of the configuration. Simulation analysis demonstrates that the result of the SFM is consistent with that of the theoretical calculation, which also confirms the effectiveness and accuracy of the two methods applied in the nonisomorphic configuration enumeration of the modular reconfigurable robot.

Automatically Deployable Robust Control of Modular Reconfigurable Robot Manipulators

We propose an automatically deployable robust control scheme for modular reconfigurable robot manipulators, which accounts for noisy velocity measurements, yet it maximizes the tracking performance while avoiding chattering effects. Our proposed control approach automatically adapts to any of the possible robot compositions of given sets of modules. The robust stability is guaranteed by exploiting the use of a recursive Newton-Euler scheme with interval arithmetic computations. Moreover, the robust performance is maximized via an online regulation of the control parameters by analyzing the power spectral density of the commanded torque signal. Being fully automatic, the proposed approach allows for a quick deployment and reconfiguration of modular reconfigurable manipulators. The algorithm is validated via simulations and experiments on a commercially available robot.

Assembly Configuration Representation and Kinematic Modeling for Modular Reconfigurable Robots Based on Graph Theory

A Modular Reconfigurable Robot (MRR) composed of standard joint and link modules has the advantages of rapid changeover of assembly configurations for a diversity of application requirements. To tackle the kinematics analysis issues for an MRR, it is essential to develop a generic method to mathematically represent all possible assembly configurations and automatically generate their kinematic models. In this paper, two types of robot modules, i.e., revolute joint modules and rigid link modules, are considered as the basic building blocks of an MRR. The topological structure of an MRR is represented by a graph, termed an Assembly Graph (AG), in which all robot modules, regardless of their types, are treated as vertices, while the connecting interfaces between any two robot modules are treated as edges. Based on graph theory, a modified adjacency matrix, termed an Assembly Adjacency Matrix (AAM), is proposed to represent the assembly configuration of an MRR, in which the three-dimensional assembly information is specified with connecting port vectors for the adjacent modules. A path matrix derived from the AAM of an MRR is employed to describe the connecting sequence of its constituting modules. The local frame representation of the Product-of-Exponentials (POE) formula is employed, which is configuration-independent. Therefore, for an MRR configuration represented with an AAM, its kinematic model will be automatically generated according to its path matrix. The proposed assembly configuration representation and kinematic modeling method are validated through a dual-branch MRR configuration.

Distributed System for Objects Localization in the Working Area of a Modular Reconfigurable Mobile Robot

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.

Palindromic, periodic and Möbius Rubik’s snakes

A Rubik’s Snake is an interesting toy which can be thought as a serial chain with applications in the construction of reconfigurable modular robots. In this paper, we present some theorems related to a Rubik’s snake with palindromic, periodic and Möbius properties. Examples are given for shape design using such properties.

Configuration analysis of a chain-type reconfigurable modular robot inspired by normal alkane

Normal alkane is an unbranched alkane whose structural formula is H-CH2-CH2-…-CH2-…-CH2-H, which can be regarded as a reconfigurable chain-type structure composed of -CH2- modules. Inspired by normal alkane, a normal-alkane-like re-configurable modular robot (NAR) is proposed. The module consists of two differential gear trains mounted orthogonally. Each differential gear train contains two input degrees of freedom and two output degrees of freedom. Due to the genderless interface design, multiple modules can be assembled into chain-type configuration. With the genderless interfaces and flexible degrees of freedom, NAR can be reconfigured into different dimensions of spatial configuration. The bond matrix is used to describe the configuration, which represents the bond attitude of the adjacent connected modules. In addition, full interconnected geometric feature (FIGF) algorithm is proposed for non-isomorphic configuration enumeration and judgment. The configurations with three modules are simulated and the results verify the feasibility of the algorithm. Finally, a prototype with three modules is fabricated and the configuration motion sequence is demonstrated.

Sliding mode-based online fault compensation control for modular reconfigurable robots through adaptive dynamic programming

In this paper, a sliding mode (SM)-based online fault compensation control scheme is investigated for modular reconfigurable robots (MRRs) with actuator failures via adaptive dynamic programming. It consists of a SM-based iterative controller, an adaptive robust term and an online fault compensator. For fault-free MRR systems, the SM surface-based Hamilton–Jacobi–Bellman equation is solved by online policy iteration algorithm. The adaptive robust term is added to guarantee the reachable condition of SM surface. For faulty MRR systems, the actuator failure is compensated online to avoid the fault detection and isolation mechanism. The closed-loop MRR system is guaranteed to be asymptotically stable under the developed fault compensation control scheme. Simulation results verify the effectiveness of the present fault compensation control approach.

A Modular Reconfigurable Robot for Future Autonomous Extraterrestrial Missions

This study proposes a heterogeneous modular reconfigurable robot called SABER (short for Step, Assembler, and Bridge Explorer Robot) that is suitable for future autonomous extraterrestrial missions. SABER comprises a platform and a reconfigurable rail and can operate in monowheel, rail trolley, and manipulator configurations. The monowheel configuration provides locomotion at a top speed of 10 km/h. The rail trolley configuration allows the robot to traverse gaps whose length is greater than its wheel diameter, climb steps whose height is no taller than the wheel radius, and pass through passages narrower than the wheel diameter. The manipulator configuration enables the robot to manipulate objects using two robotic arms with changeable tools. This design allows several SABERs to work as a team to enlarge their working area or enhance their mechanical capabilities. As such, SABERs can undertake various tasks in extraterrestrial missions, including exploration, outpost building and equipment maintenance. The key feature of the SABER is its mechanical transmission that allows its platform to move rapidly along a rail made from the manipulators of the robot. We also formulated the novel concept of a jamming safety diagram that is used to determine controller precision requirements to prevent the transmission from jamming. Finally, a new positioning controller meeting those requirements was introduced and implemented as field-programmable-gate-array firmware that is compatible with a wide range of low-cost integrated circuits. In numerical simulations, we evaluated SABER with respect to its speed, acceleration, oscillation, and ability to negotiate gaps and steps; SABER performed as well as or better than existing autonomous mobile robots and modular reconfigurable robots.