Continuously bending reconfigurable robot manipulators for flexible handling and assembly in confined and remote environments
Lead Research Organisation:
Imperial College London
Department Name: Design Engineering (Dyson School)
Abstract
The majority of serial robots use traditional rigid-link designs with multiple joints and links [1]. However, for multiple individual tasks that are performed by these robots in reduced spaces, a lower number of degrees of freedom (DOF) is sufficient [2]. This includes activities such as manufacturing electronics and offshore operations, where working inside reduced spaces and in remote locations is vital. Other examples of such situations are deep sea, hazardous material handling, and space robotics. Whilst sufficient for the task, a low DOF limits the workspace, and therefore the flexibility of the system, hindering the ability for the robot to adapt to various tasks. For work within remote areas that requires complex positioning, a traditional robot arm with higher DOF seems more appropriate for instance, as a higher DOF allows the robot arm to adapt to given scenarios, accomplishing a larger range of complex tasks provided. Nevertheless, a higher number of DOF causes the robot to be larger, heavier, and sometimes more complex than necessary for particular activities. This can cause specific limitations when robotic requirements are needed to be met, for example weight limitations with space robotics. The ideal solution to this problem therefore is a simpler, low DOF robot that maintains the flexibility of the system.
Soft robot arms, implemented usually using a single continuously bending link, promise a number of improvements over stiff, discrete manipulators such as reduced size and weight requirements with an increase in system flexibility; however, these robotic systems have been struggling to achieve the holding strength and precision of fully rigid designs [3]. Recent research has explored the use of variable stiffness links in soft, continuum robots for surgery, which contains aspects of both systems by varying the rigidity of the robot [4][5]. This development allows the robot to overcome the strength limitation of soft robotics, by providing a rigid platform when the robot is 'activated'. However, at present, no robots with a reduced number of DOF that can be adaptable to multiple tasks with variable but controllable workspace exist; these robots are a need for the automation of processes and the augmentation of human operator capabilities in confined and remote environments.
This research aims to combine, improve, and extend existing research in soft robotics for use in reconfigurable serial arms, producing robots with a reduced number of DOF that can adjust their topology using variable stiffness links, thus being able to perform a range of tasks with a focus on handling and pickand-place assembly operations. Ideal implementations of these systems would be as collaborative robotics in operations that require a reduced size/weight robot with a high DOF performance, namely deep sea and space robotics. These novel manipulators have the possibility of greater flexibility by adapting to different workspaces while keeping the benefits of a lower DOF robotic system, such as weight, size, and control complexity. The proposed robots will be fabricated using serial chains of extrinsic malleable links: A variable stiffness, flexible, continuously bending link which can be repositioned by hand when in a non-rigid state, while holding its position when activated. These malleable links will be connected by revolute joints to be able to perform the operations that can be carried out with traditional robotic arms.
Soft robot arms, implemented usually using a single continuously bending link, promise a number of improvements over stiff, discrete manipulators such as reduced size and weight requirements with an increase in system flexibility; however, these robotic systems have been struggling to achieve the holding strength and precision of fully rigid designs [3]. Recent research has explored the use of variable stiffness links in soft, continuum robots for surgery, which contains aspects of both systems by varying the rigidity of the robot [4][5]. This development allows the robot to overcome the strength limitation of soft robotics, by providing a rigid platform when the robot is 'activated'. However, at present, no robots with a reduced number of DOF that can be adaptable to multiple tasks with variable but controllable workspace exist; these robots are a need for the automation of processes and the augmentation of human operator capabilities in confined and remote environments.
This research aims to combine, improve, and extend existing research in soft robotics for use in reconfigurable serial arms, producing robots with a reduced number of DOF that can adjust their topology using variable stiffness links, thus being able to perform a range of tasks with a focus on handling and pickand-place assembly operations. Ideal implementations of these systems would be as collaborative robotics in operations that require a reduced size/weight robot with a high DOF performance, namely deep sea and space robotics. These novel manipulators have the possibility of greater flexibility by adapting to different workspaces while keeping the benefits of a lower DOF robotic system, such as weight, size, and control complexity. The proposed robots will be fabricated using serial chains of extrinsic malleable links: A variable stiffness, flexible, continuously bending link which can be repositioned by hand when in a non-rigid state, while holding its position when activated. These malleable links will be connected by revolute joints to be able to perform the operations that can be carried out with traditional robotic arms.
Organisations
Publications
Clark A
(2019)
Assessing the Performance of Variable Stiffness Continuum Structures of Large Diameter
in IEEE Robotics and Automation Letters
Clark A
(2020)
Design and Workspace Characterisation of Malleable Robots
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509486/1 | 01/10/2016 | 31/03/2022 | |||
| 2286512 | Studentship | EP/N509486/1 | 01/10/2017 | 31/07/2021 | Angus Clark |
| Description | This research has introduced the new concept of 'Malleable Robots', a type of reconfigurable robot arm that can adapt to the task at hand. Specifically, this area of robotics allows for the reduction of the joints of the robot such that only the 'necessary' joints are kept, unlike typical robot arms which are constructed from more joints than necessary for a task to make the robot adaptable across tasks. A key development of this research is the enabling technology of malleable robots, known as malleable links, which are variable stiffness continuously bending flexible limbs that are used to connect the joints of the robot. These can transition between flexible and stiff and allow the robot to modify the position of its joints. Developed as part of this research, multiple methods for achieving malleable links were explored and evaluated, with links constructed from layer jamming sheets proving to perform the best. This was demonstrated through another achievement of this research, which was the creation of a set of metrics for assessing and evaluating variable stiffness links with respect to their performance as malleable links. Following the development of the malleable robot, the definition of the defining kinematics, the equations that allow the robot to move and position itself accurately, of the robot were discovered. Due to the adaptable nature of the malleable robots, typical solutions for the kinematics were not possible. Along with this, a new method was described for determining an optimal configuration of the malleable robot based on a given task. Finally, in achieving said configuration, an augmented reality application was developed to guide the user through configuring the malleable robot, and to present to the user (using holograms overlapping the real robot) information for how modifications to the malleable robot affect its characteristics. |
| Exploitation Route | One limitation of malleable links was the lack of integrated sensing, enabling the direct measurement and monitoring of the curvature of the malleable link. While this is an area that is not unfamiliar in continuum robot research, it is largely unexplored in large diameter variable stiffness links used in malleable robots. The malleable links presented in this research are all of the extrinsic type, where they are reshaped through an external means, such as a user manually reconfiguring the link. An intrinsic link would provide the advantage that user interaction is not required, as the link is capable of reshaping itself. For more complex tasks, such as those requiring certain end effector orientations or paths, a higher DOF robot is necessary. Higher DOF malleable robots are possible, and their resulting workspaces and reconfiguration environments are of significant interest. We demonstrated a couple a methods using distance geometry for computing the optimal topology reconfiguration of a malleable robot based on either a desired end effector location and orientation, or multiple end effector locations. For future work, solving the problem of computing an optimal topology reconfiguration using alternative methods that do not require converting to a system of polynomials can be performed. |
| Sectors | Manufacturing, including Industrial Biotechology |