Cable-driven parallel Robots for Agile operations in manufacturing FaciliTies – CRAFT
Cable-Driven Parallel Robots for Agile operations in Manufacturing Facilities
The CRAFT project aims to design, model and control Cable-Driven Parallel Robots (CDPRs) for agile operations in manufacturing facilities. The CDPRs developed in CRAFT will: (i) work in cluttered environments, (ii) be autonomous, (iii) allow the user to co-manipulate large and/or heavy objects. An important obstacle to the dissemination of CDPRs is a lack of standards. Hence, another objective of CRAFT is to define some standards for CDPRs that will be submitted to regulation authorities.
Design, modeling and control of CDPRs for agile operations in manufacturing facilities
Cable-Driven Parallel Robots (CDPRs) form a particular class of parallel robots whose moving platform is connected to a fixed base frame by cables. The performance improvement of CDPRs is still a challenge because the cable unilaterality (cables can pull but cannot push) makes their analysis much more complex than parallel robots with rigid legs. To address those challenges we will develop an appropriate software framework of numerical solving methods, whose validity will be verified on realistic experiments. The integration of theoretical modeling, numerical solving and experiments will result in strong technological and scientific advances on the topic. <br /><br />We aim therefore at developing agile CDPRs, called Reconfigurable Cable-Driven Parallel Robots (RCDPRs. From a mechanical point of view, changing the CDPR geometry is relatively easy either by moving the winches, by using pulleys to modify the location of the winch exit points or by changing the location of the cable attachment points on the platform. We aim at developing a design framework that takes as inputs the task requirements and a description of the CDPR environment. <br /><br />The CRAFT project aims to design, model and control CDPRs for agile operations in manufacturing facilities. The CDPRs developed in the framework of this project should be able to work in a cluttered environment and assist operators in carrying and manipulating large and heavy parts. Therefore, the CDPRs under study will have two working modes. The robots will either be autonomous (with possibly some human operators in its environment) and will realize some tasks that are set up offline or the user will safely co-manipulate large and/or heavy objects with the cobot in large and cluttered environments. The robots developed in the framework of the CRAFT project will provide the user with a good agility in large workspace while ensuring the safety of the human operator. Here, the motions of the objects are supposed to be slow and adapted to the identified risks. One challenge about the user safety lies in the HMI (Human Machine Interface) design such that the safety integrated in the CDPR will guarantee that the CDPR control is performed in a safe manner by the user. Currently there is a lack of advanced specifications about HMI in the robotics standards (EN ISO 10218-1), especially to control robots in safe state during their human guided mode in an ergonomic manner. There is also a lack of safe ergonomic devices on the market. Another important obstacle to the dissemination of CDPRs, in spite of their large potential impact, is a lack of standards. Indeed, existing rules regarding lifting apparatus are mostly not appropriate for CDPRs that use a very different technology. Hence another objective of the CRAFT project is to provide the data requested for defining standards for CDPRs that will be submitted to regulation authorities.
CRAFT aims to design, model and control CDPRs for agile operations in manufacturing facilities. The originality and relevance of CRAFT project with respect to the state-of-the-art mainly lie in (i) the integration of theoretical modeling, numerical solving for agile CDPRs while considering complex cable models and uncertainties and (ii) the determination of standards so that agile CDPRs can be accepted in industry. The scientific objectives of the CRAFT project are described thereafter:
1) Design strategy of reconfigurable CDPRs: The robots studied in the framework of CRAFT project will be reconfigurable because they should be easy to deploy and install and should be adapted to the task to be realized and the environment.
2) Kineto-static models of CDPRs: Determining the relationships between cable lengths and platform pose is crucial for controlling CDPRs. A more realistic cable model will be considered. Besides, an analysis of the influence of uncertainties will be performed
3) Identification of CDPR physical parameters: Solving the kineto-static models and designing an efficient model-based control requires an accurate estimation of CDPR parameters such as geometry, elasticity of the cables. Therefore, original methods will be developed in the CRAFT project to identify those parameters either during the robot operation whenever possible or during the maintenance phases.
4) CDPR control strategies: CDPRs have the property that their state equations change according to the robot configuration. Hence adaptive control schemes are required and will be synthesized in the CRAFT project. Furthermore, we will develop control strategies that allow the robot to switch from an “autonomous” mode to “co-manipulation” one.
5) Joint action: The acceptability of the CDPRs by the user and the ergonomic improvement of working condition thanks to robots developed during the CRAFT project will be studied.
6) Standardization: An important obstacle to the dissemination of CDPRs, despite their large potential impact, is the lack of standards. Therefore, some standards to be respected by CDPRs for agile and co-manipulation of parts will be defined in CRAFT.
7) Prototyping and experimentations: The technical solutions developed to ensure safety (in both CDPR “autonomous” and “co-manipulation” modes) and to improve the ergonomic aspect (HMI) will be implemented on the two prototypes developed in the scope of CRAFT. Accordingly, we will tend towards technical solutions that can be used in industry, using new ergonomic and safe control devices. In addition, feedback on the implementation of safety devices (actually on market or new and developed in this project) will directly provide normative recommendations.
A major application of CDPRs is industrial manipulations, especially for large/heavy parts, possibly with an interaction with human workers. However CDPRs offer a high potential for applications that go well beyond manufacturing and another huge application field for CDPRs is service robotics. The development strategy proposed in the CRAFT project can be transposed in this field without any modification except for user acceptance that is more domains dependent. On the other hand, the reconfigurability strategy proposed in the CRAFT project is especially appropriate for service robots that evolve in a more constrained environment than industrial robots.
Combined with the relatively low dangerousness of cables, CDPRs provide the user with a high level of safety. Furthermore usual cobots are relatively expensive even for small load (typically 80 000$ for a load of 100 kg) with a relatively limited workspace while CDPRs may offer a much larger load that can be moved over very large workspaces for the same price.
The low intrusion of cables and their relatively low dangerousness are an important safety factor for human workers working in their vicinity. Human acceptance may also be improved because of the low intrusion of cables (compared to rigid legs) and of the whole system.
Moreover, CDPRs offer an interesting “test bed” for synthetic cables that are not yet used in lifting apparatus because of a lack of standards. Hence they will contribute to provide realistic data regarding wear, performance evolution over a long period and over a set of environments.
CDPRs offer low-cost agility and flexibility even in the case of very large systems. Indeed, even in case of failure of one cable, CDPRs will lose only one degree-of-freedom: this constitutes an additional safety factor. In addition CDPRs energy efficiency is estimated to be at least 25% better than classical robots and they have much less parts, leading to lower cost, especially if the workspace size is taken into account.
Another objective of CRAFT is to show once again that CDPRs are efficient in realistic environments, but also to provide data and to contribute to the establishment of new standards. Experimental validations will allow us to assess in an objective manner the improvements of the new CDPR models developed in the CRAFT project.
We sincerely believe that combining the theoretical work and experiments is an asset for creating a breakthrough in lifting apparatus. Our contributions to both CDPR standardization and human acceptance will be also a major step for dissemination.
The expected results are significant advances in the development of tools for the design, modeling and control of reconfigurable and agile CDPRs able to work in both autonomous and co-manipulation modes. Our contributions to both CDPR standardization and human acceptance will be also a major step for dissemination.
Our contributions to both CDPR standardization and human acceptance will be also a major step for dissemination. Those results will be communicated in both peer-reviewed papers published in leading journals such as ASME Journal of Mechanisms and Robotics, Mechanism and Machine Theory, IEEE Transactions on Robotics, Journal of the Human Factors and Ergonomic Society (SAGE), ACM Transactions on Human-Robot Interaction (ACM), IEEE Transactions on Systems, Man, and Cybernetics, Part B (Cybernetics) and international conferences such as the fourth and the fifth International Conference on Cable-Driven Parallel Robots, ASME IDETC, IEEE ICRA and IEEE IROS.
Moreover, the obtained results will be communicated to PhD and Master Students through some schools and workshop in which the project partners will teach such as the Workshop on Parallel Kinematics Machines, the “Ecole Thématique du GdR Robotique”.
The CRAFT project aims to design, model and control Cable-Driven Parallel Robots (CDPRs) for agile operations in manufacturing facilities. The CDPRs developed in the framework of this project should be able to work in cluttered environments and assist operators in carrying and manipulating large and heavy parts. Therefore, the CDPRs under study will have two working stages. On the one hand, the robots will be autonomous and will realize some tasks that are set up offline. On the other hand, the user will co-manipulate large and/or heavy objects with the robot in large and cluttered environments. Accordingly, the robots developed in the framework of the CRAFT project will provide the user with a good agility in large workspaces. Existing rules regarding lifting apparatus are mostly not appropriate for CDPRs. Hence another objective of CRAFT project is to define some standards for CDPRs that will be submitted to regulation authorities.
The main expected contributions of the CRAFT project are the following:
1. Design strategy of reconfigurable CDPRs
2. Kineto-static models of CDPR while considering complex and realistic cable models
3. Identification of geometric and elastic parameters of CDPRs
4. Development of control schemes for the CDPRs to be able to work in both “autonomous” and “co-manipulation” modes while guaranteeing safety
5. Joint action: The acceptability of the CDPRs by the user and the ergonomic improvement of working condition thanks to robots developed in this project will be studied.
6. Standardization: Work on standardization is of the utmost importance to achieve industrial operations both for autonomous manipulation and co manipulation of large and/or heavy parts with CDPRs.
7. Prototyping and experimentations
Project coordination
Stéphane CARO (Laboraroire des Sciences du Numérique de Nantes)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Partner
Inria Centre de Recherche Inria Sophia Antipolis - Méditerranée
LS2N Laboraroire des Sciences du Numérique de Nantes
CETIM CENTRE TECHNIQUE INDUSTRIES MECANIQ
Help of the ANR 377,574 euros
Beginning and duration of the scientific project:
January 2019
- 36 Months
