Review article

The internet of modular robotic things: Issues, limitations, challenges, & solutions

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Jean-Paul A. Yaacoub, Hassan N. Noura, Benoit Piranda

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https://doi.org/10.1016/j.iot.2023.100886Get rights and content

Abstract

The world is becoming more digitised with the rise of modular robotic systems. Therefore, with the increasing demands and needs for robotics, the modular robotic domain was introduced as an essential key part of Internet-of-Things (IoT). Modular self-configurable robotic systems (E.g. swarms) are classed as “smart” autonomous machines with kinematic properties, defined by a set of interconnected links, modules and algorithms to achieve the required three-dimensional (3D) or two-dimensional (2D) complex shape or hierarchical structure. Due to its “intelligent” concept, it beame suitable for its deployment in the Internet of Robotic Things (IoRT) domain. Thus, becoming a key part of it and establishing itself as the newly revolutionised Internet of Modular Robotic Things (IoMRT). This paper presents a survey that highlights and discusses this novel IoMRT concept that focuses on self-reconfigurable modular robots and robotic systems by discussing their criteria, characteristics, architecture, and design. The security, safety, and privacy aspects are also presented and discussed, making it among the first papers to focus on this topic and its future. Moreover, the main drawbacks and challenges are also highlighted, while the already available solutions are also presented and analysed. A brief analysis regarding each solution is also presented with an insight into their future work. Additionally, more work was presented regarding the security aspect(s) of modular robotic systems to protect them from possible cyber or/and physical attacks. Thus, covering all possible aspects of the IoMRT.

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Introduction

The adoption of Modular Self-Reconfigurable Robots (MSRR) and robotic systems into the IoT to establish the Internet of Modular Robotic Things (IoMRT) concept which includes the Internet of Swarm Robotic Things (IoSRT), have offered a variety of diverse but unique solutions that answer the ongoing growing demands, especially in the domain of IoT. This include but not limited to real-world applications in medical, military, law enforcement, economic, space exploration, business, agricultural and cyber–physical domains. Self-reconfiguration and self-healing capabilities are among the most requested demands due to their unique capabilities to overcome the limitations of traditional robotic systems, especially in terms of power consumption and time, and with the least need for any human intervention(s). In IoT, unlike traditional robotic systems, modular self-reconfigurable robots offer a unique advantage in terms of re-usability, cost, size, reconfiguration, and resource consumption, along the ease of manufacturing and use with the ability to operate within complex environments to achieve complex 3D shapes also with the least human intervention.

In fact, the development of novel MSRRs remains one of the biggest challenges and constraints to overcome despite the main characteristics and offered advantages. Hence, this paper offers an analytical view on the MSRR, while domain taking into consideration and account the importance of the security aspect and the main threats and risks that lurk around and surround each aspect of this domain. Moreover, approaches that were presented by different fellow researchers are also presented, highlighted and analysed to offer an insight and a brief comparison on each presented work including mainly prototypes, modules, and algorithms. As the robotic domain within the IoT field is further shifting towards the modular concept while adopting the swarms’ methodology, another field is starting to emerge which is the Internet of Swarm Robotic Things (IoSRT), and together combined with the IoMRT, the Internet of Modular Swarm Robotic Things (IoMSRT) will emerge and rise in the near future, with the ability to communicate (homogeneously/heterogeneously) and to perform tasks accurately and autonomously, while being capable of self-correcting, self-configuring and self-healing.

Designing Modular Self-Reconfigurable Robots (MSRR) and Modular Self-Reconfigurable Robot Systems (MSRRS) is a challenging task especially when it is part of IoMRT. However, it is also a very rewarding one since it can shape the future aspect of modular and non-modular robotic systems in the robotic field and IoT domain alike. The future of robotic systems lies within the two main notions of self-reconfiguration and self-healing processes to accurately achieve a higher level of robustness, flexibility and adaptability respectively.

This work aims to present a detailed study over the MSRR and MSRRS and their link to IoT to highlight the importance of their adoption in real-world and real-time IoT applications in the foreseen future. This will help with identifying and overcoming unforeseen situations and ensuring long-term self-sustaining robotic systems mainly capable of performing self-healing, self-reconfiguration and self-replication tasks. At the same time, this paper also aims to highlight the main drawbacks, challenges, threats and attack aspects that may target the modular robotic systems to offer a secure, safe, accurate and error-free IoRT and IoMRT domains and shedding the light on the future of IoMRT which is will be combined with the IoSRT to introduce the IoMSRT.

In fact the integration of this new concept will help to outsource both components and programming, and ensure the software compatibility with the Application Programming Interface (API). At the same time, to also visualise the impact of the Inertial Measurement Unit (IMU) selection on the modular embedded system’s total performance. The objective is for it to be achieved at a lower computation and programming times and at reduced costs with more affordable solutions being presented. As the world gets more smarter and more connected, more computing power is being added into smaller modular robotic devices. Nonetheless, both modular robots and drones now represent the intersection between embedded software and the modular robotic components. Both of them include software and hardware modules, high processing power, cameras, multipurpose/specialised sensors, and electro-mechanical components [1]. Despite them being complex to build and program, except that they are being extensively used to develop new prototypes that allow their deployment in real-life to deal with real case scenarios [2] and applications [3], [4]. This is mostly due to the collective behaviour of swarm intelligence and decentralised, self-organised systems.

This paper introduces a novel new IoT concept which complements the IoRT domain and overcomes its main limitations and challenges. The newly introduced concept is called Internet of Modular Robotic Things (IoRT), which allows swarms of autonomous robots [5] and distributed systems with local sensing and communication capabilities, which are part of IoSRT, to be connected to a centralised and well-defined access control to enhance the connection, synchronisation and communication with each other, which is one of the main other “collective behaviour” limitations for swarms robotics [6], [7]. Another limitation that the IoMRT can overcome is the terrain problem and environmental conditions that prove to be challenging. A problem that is mitigated within the IoMRT domain, offering more flexibility and adaptability to any environmental and geographical changes.

Moreover, this paper also examines the newly introduced concept and compares it with the IoRT domain especially in terms of safety, security, accuracy and privacy aspects that can be linked to the modular robotic domain and IoT, including challenges and vulnerabilities/security gaps [8], [9], [10]. Future work is also presented concerning IoMRT, and several lessons that were learnt, are being learnt and to-be-learnt are also presented and explained. Moreover, several suggestions and recommendations are also presented in this regard to take precautionary and protective measures and procedures, especially when adopting the IoMRT domain and the modular robotic design.

The real aim is to propose this new concept as an advanced version of the IoRT, which takes into consideration the main limitations of robotic systems and aim to solve them through the reliance on the modular robotic concept. However, it is also important to highlight the main drawbacks, attacks and challenges that surround this newly introduced domain with an insight about how the future of IoT is going to be once this IoMRT concept is introduced and applied. More light was also shed on the swarm robotics which are to be further integrated to form another new IoRT concept which is the IoSRT. Additionally, this work also highlights the future of modular robots and swarms combined which will merge both concept to allow the emergence of the IoMSRT.

This paper presents an advanced up-to-date study on the self-reconfiguration of modular robots and robotic systems including swarm robots, which were mentioned, highlighted and discussed by various papers [11], [12], [13], [14]. Moreover, the paper extends the presented work in [15], [16] and has worked on gathering the most related and recent structures and algorithms to the modular self-reconfigurable robotic domain. Further research was also conducted regarding the main modular robotic systems’ characteristics and applications mentioned in [17], in addition to their limitations and challenges discussed in [18], with more complementary information being added, and more details with examples being presented. Both Claytronics and self-assembly concepts which were presented in [19], [20], are further studied and detailed (Section 9.5). Also, the idea of programmable matter, presented in [21], [22] is further explained. Other key concepts related to self-organisation and self-adaptability which were mentioned in [23], [24] are further detailed and described in this paper.

In addition to all of the mentioned above, this paper further contributes by presenting its added work in the following list:

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Security Concepts: this paper presents, highlights and classifies the IoMRT, especially from a security point of view and safety concept, by discussing available solutions and proposing others.

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Cyber–Physical Security Aspects: this paper generally takes into consideration the main threats and risks that affect the modular robotic domain especially in terms of self-reconfiguration, as well as the most prominent type of attacks that may potentially target the modular robotic domain (i.e eavesdropping, packet interception/manipulation, misconfiguration, etc.).

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Modular System Mapping: the whole modular robotic system mapping is also presented and divided into four main parts which are: Operator, Gateway, Communication and Modular Robot, (see Fig. 12) to present a clear illustration of the IoMRT domain.

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Proposed IoMRT’s Components Security Framework: an IoMRT security framework is also presented to highlight the main attacks and weaknesses of every IoMRT component, as well as the most suitable and ideal security measures and countermeasures.

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Safety & Privacy Aspects: both safety and security best practices of modular robotics systems for IoT are presented and discussed to achieve the needed trade-off without affecting their performance.

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Proposed System Mapping Security Framework: that takes the Defense-in-Depth (DID) the main possible security solutions that can be applied as active measures and countermeasures against Attack-in-Depth (AID) cases that actively targets IoMRT and their Modular Robots components.

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Drawbacks & Challenges: limitations, drawbacks and challenges that surround the current and future states of modular robotic systems are presented and discussed.

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Self-Reconfiguration Aspect: this paper presents the main characteristics, components and advantages that surround the self-reconfiguration domain in modular robots and robotic systems.

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Risk Assessment: this paper presents a risk assessment methodology that can be adopted once the security aspect and concept are grasped by modular robotic systems and robots in order to mitigate threats and reduce both likelihood and impact of any given risk.

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Threat Identification: this paper identifies threat source, types and also classifies them in an easy-to-understand manner so its easier to track them and mitigate them.

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Presented Solutions: this paper presents, discusses and analyses most of the modular reconfigurable and self-reconfigurable robots and robotic systems solutions including recent and up-to-date solutions.

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Modular Robotic Classification: which is presented based on their movement and module types, structure, and communication nature.

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IoSRT future concept: the IoSRT concept is also highlighted as it will be a key part of the future of IoT alongside with the IoMRT, where the full focus is on the IoMRT, before taking this concept and applying it into the IoSRT by merging swarm modular self-reconfigurable robotic systems into the IoT.

This paper is divided into ten sections aside the introduction in Section 1, and is presented as follows: In Section 2, modular robotic systems are presented and discussed, along with their main components, characteristics, classification, modular robot types, taxonomy of architecture, IoMRT-related applications and its main properties. In Section 3, the self-reconfiguration process is presented and discussed, including its main criteria, characteristics, advantages, and main types. In Section 4, the IoMRT communication nature is presented including its communication layers, in addition to modular robotics layers, along with their protocols, and communication algorithms. In Section 5, possible IoMRT networking topologies are presented. Section 6 discusses the main IoMRT’s limitations, constraints, failures and challenges. Section 7 presents the IoMRT’s security concept and addresses its main security issues and safety concerns. Moreover, the main security threats are presented, including the main threat source, type and nature, while the main security vulnerabilities are discussed. Security attacks are also presented including the attack source, type, classification, and their main targeted IoMRT components. In Section 8, the IoMRT risk concept is introduced, where the main type and causes of risks are identified, while a risk life-cycle is presented including risk planning, management, assessment, and analysis, in addition to the most suitable risk mitigation methods. Section 9, presents, discusses and analyses the modular robotic systems solutions including theoretical, mobile, frameworks, modular, algorithmic and robotic security solutions. Section 10 is dedicated to proposing our main suggestions and recommendations especially in terms of security, safety, privacy and availability, as well as the main lessons learnt from previous non-modular robotic domains to offer a safer and more secure usage and adoption of security measures in the modular self-reconfigurable robotic domain. Additionally, future work is also presented to give an insight into the evolution of this new IoT-related domain, as well as security/safety-related suitable solutions. Section 11, concludes this paper work and provides insight into the future of this new IoMRT domain.

Section snippets

Modular robotic systems

Modular robotics can be described as smart autonomous objects that come in the form of a 2D or 3D shape, capable of sensing their surrounding and communicating with each other via actuators to perform a variety of physical tasks (i.e moving), visual (i.e colour changing) or/and audio tasks (i.e sound) [14]. For this reason, it is important to understand its main components, along with the state of art of self-configuration algorithms and underlying models in modular robotic and self-organising

Self-reconfiguration process

”Self-reconfiguration” means that a given IoMRT device can use its own control system to change its overall shape. This term is often accompanied with the ”modular” concept where a modular robot is made up of a set of identical modules (often in a lattice structure) that can be attached or detached from the main modular robotic system. In fact, self-reconfiguration means changing the shape made by the global set of robots, or changing the total space covered by the ensemble of robots.

In the

Communication nature & technologies

In fact, communication is a key and essential part that the modular robotic domains within the IoT field rely on to establish connections either physically or wirelessly to perform the necessary tasks. The proposed communication system can be divided into two main parts: IoMRT connection based on operator-to-modular robots, and Modular robots connection based on modular robot-to-modular robot (see Fig. 14). In the following, we present and discuss the main communications technologies that are

IoMRT algorithms

Modular robots rely on a variety of algorithms depending on the task’s complexity especially when integrated into the field of IoT, to ensure a much more effective IoMRT environment, including algorithms that may possibly be integrated in the future. As a result, machine-learning-based, application layer-based, as well as other algorithms are presented and discussed (see Fig. 10).

IoMRT: Limitations, failures & challenges

In IoMRT, robotics [138], [139] including self-reconfigurable modular robotics and robotic systems are often being adopted into a variety of Internet of Things (IoT) domains such as Medical and Industrial IoT [32], [33]. As a result of such adoption, they are left prone to a variety of attacks, limitations, and challenges.

IoMRT security

Modular self-reconfigurable robots, like any other robotic system linked to the IoT domain, are also susceptible and prone to the same security issues, threats, vulnerabilities and attacks that target the IoRT. For this reason, this section has been introduced to highlight and discuss the main security issues and concerns that surround the IoMRT, in addition to the main threats and vulnerabilities, along with the main security attacks, which are presented as follows: However, before starting,

IoMRT-related risks

The aim of this part is to highlight the main IoT issues, vulnerabilities and attacks that surround and target the modular robotic systems (IoMRT) specifically, and the robotic domain (IoRT) generally. This adoption, despite having a huge positive impact with a greater contribution to the improvement of IoT sectors, except that it left the modular robotic systems prone to larger variety of risks and threats. In fact, an IoMRT proposed risk assessment work is summarised in Fig. 15. Therefore,

Presented modular robotic systems solutions

Several existing solutions were presented in order to ensure that the proprieties of self-reconfiguration of Modular Robotic Systems (MRS) especially in IoT domains such as IoRT and IoMRT, respectively. For this reason, this section presents and discusses the different types of available solutions that adhere to different limitations, challenges and drawbacks that surrounds the 3D modular robotics domain.

Suggestion & recommendation:

This paper takes into consideration both IoRT and IoMRT’s safety, privacy, and availability aspects from a security point-of-view regarding the modular robotic systems to ensure their safe and secure use ahead of their deployment in real challenging and changing environment adopting complex scenarios. This concept is adopted to avoid ambiguity regarding the concept that safety and security mean the same thing, which is not true. Also, the main learned lessons are presented.

The whole work is

Conclusion

As modular robots evolve into a swarm formation and start the adoption of the swarm concept, the robotic domain within the IoT field is being reshaped and re-innovated in a way that allows it to fulfil new gaps and accomplish new tasks. The modular concept, within the IoT, has been since addressing new challenges and overcoming the limitations of other non-modular robots with higher success rates, less time and fewer resource requirements. As a result, this paper has presented a survey that

Declaration of competing interest

This paper is funded by the EIPHI Graduate School (contract “ANR-17-EURE-0002”).

Table of Contents

Section snippets