Soft continuum robots are made of materials such as silicone and are characterized by the fact that they can deform continuously. The materials used have stiffnesses comparable to human tissue and enable a high degree of adaptability and flexibility. These properties allow soft continuum robots to navigate through confined spaces and interact with objects and living beings without damaging themselves or their surroundings.
Soft continuum robots for new requirements
Such requirements are placed on robots in medical robotics and in disaster areas, for example, where conventional robots reach their limits. In medical robotics, for example, advanced technologies are needed that can adapt to the anatomy and requirements of the human body. In disaster areas, systems are needed that can navigate through narrow crevices and gently rescue victims. Soft continuum robots can make a contribution here.
The continuous deformability of soft continuum robots is accompanied by new challenges for the design and application of these systems. Model-based methods for structural synthesis and control, for example, are still in their infancy.
The Soft Material Robotics Toolbox (SMaRT) research project is a collaborative project that deals with precisely these challenges. It involves the Institute of Dynamics and Vibration Research (IDS), the Institute of Mechatronic Systems (imes) and the Institute of Assembly Technology and Robotics (match) at Leibniz University Hannover. The project is part of the DFG priority program Soft Material Robotic Systems and is now in its second funding phase.
Methodological toolkit for the design and application of soft continuum robots
With the SMaRT project, the scientists are creating a basis for research into soft continuum robots. The toolbox is intended to enable researchers worldwide to adapt the developed and implemented methods for their systems and applications and thus promote the use of these robots in practice. The focus is on the development of models that describe both the static and dynamic properties of these robots and are used in model-based processes such as path planning, control and design optimization.
The basis of the toolbox developed in the project is a Cosserat beam model. As a one-dimensional continuum model, it enables a detailed description of the macroscopic deformations of a soft continuum robot. The model represents bending, shear, elongation and torsion along the structure. It represents a compromise between the very accurate but computationally intensive finite element method (FEM) and the piecewise constant curvature model. The latter is computationally less complex, but also less precise, as it is based on simplifying assumptions of the kinematics.
As part of the research project, the match is investigating and further developing static models, including in particular contact with the environment, which is a core element of soft robots. Models can be used for motion planning and design optimization, for example. imes is intensively investigating the development and use of dynamic models, which are used in observers and controllers, for example. These models help to control the movement of soft continuum robots in real time. The IDS focuses on contact modeling for the materials used, such as silicones, and their integration into the beam models. This includes analyzing the material properties and their influence on the robot dynamics.
The method kit consists of several blocks. Implemented methods in Matlab – especially for the automated model setup and static simulations of the Cosserat model – enable easy familiarization and adaptation. A C++ implementation of the dynamics enables real-time capable simulations. In addition, detailed FE models in Abaqus are used for in-depth analysis and as a basis for parameter identification of the Cosserat models.
A pneumatically operated silicone robot is a case study for the validation of models and testing of algorithms. Soft actuator modules can be controlled independently of each other via three integrated air chambers. The application of compressed air leads to elongation and curvature of a module. Serially linked modules can move in space like a trunk.
SMaRT as the basis for more in-depth and application-specific development of soft continuum robots
Although SMaRT is primarily focused on basic research, there are numerous potential areas of application that could benefit from the methods and models developed. In medicine, the models developed could help to design more precise and adaptable surgical instruments that adapt to the patient’s specific anatomy. Pneumatically operated soft robots are also MRI-compatible and can assist in magnetic resonance imaging (MRI) operations. In industrial robotics, models can help design robots that can handle delicate components or work in complex environments.
SMaRT contributes to the development of soft continuum robots. Through close collaboration between the IDS, imes and match institutes, comprehensive models and methods are being developed that make it possible to design and control these robots more efficiently. The research results provide a springboard for future applications and can make robotics as a whole more flexible and adaptable.
