Robotic structures based on variable stiffness enable high-performance and flexible motion systems that are inherently safe and thus allow safe Human-Robot Collaboration. This letter presents the design of a robotic structure based on variable stiffness. A robotic manipulator is developed using three variable stiff segments based on particle jamming with a backbone architecture and two tendons for an underactuated motion control of the whole structure. By switching the structural stiffness, the manipulator is able to perform complex planar motion with only one pair of tendons, reducing the number of actuators required. A kinematic modeling approach for the calculation of the forward kinematics of this soft continuum structure is presented, and the validation on the real system is explained. The kinematic simulation is performed with a multibody simulation model (MBS) using rigid body elements in combination with rotational springs. The validation of the model is carried out with visual measurements of the real system using defined target shapes. Simulation and experimental results are discussed and compared also with a common constant curvature model. The developed MBS-model demonstrates a promising modeling approach with a position error lower 3% for the calculation of the presented manipulator under gravity.

Many living beings show the ability and necessity to develop invertible, tubular structures to enable additional functions temporarily. The biological archetypes always demonstrate a high change of volume of the structure between an inactive and active state. This makes the principle interesting for many technical applications, where a certain geometry or an additional volume has to be generated situationally for a task and can only be accepted temporarily, for example, in minimally invasive robotics. A possibility was sought to transfer the archetype into the technical context and to evaluate geometric-constructive dependencies based on an inversion of the structure. The result is a practicable design for repeatedly invertible net structures, which can be used for products with temporary additional functions and volumes.

There is a wide spectrum of injuries and medical conditions that are treated with the use of orthoses. For better comfort fully customized orthoses are designed and manufactured via 3D-printing or thermoforming thermoplastic casts with a low glass transition and softening temperature nowadays. This study aims to print a planar orthosis design and then thermoform the orthotic blank with intrinsic heating to get the final customized design depending on patient's needs. After identifying possible thermoplastic polymers for the application with differential scanning calorimetry (DSC) to determine thermal properties, tensile testing for mechanical properties and peel-off testing to measure multi material printing adhesion, the final orthosis blank is printed using Wire-EncapsulatingAdditiveManufacturing to integrate heating wires into the structure and create the intrinsic ability of heat generation for the thermoforming process.

Using a newly developed tool head with an additional rotational axis and a wire feed, wires can be directly processed in the fused filament fabrication (FFF) process. Thus, electrical structures such as conductive paths, coils, heating elements, or sensors can be integrated into polymer parts. However, the accuracy of the wire deposition in curved sections of the print track is insufficient. To improve the wire position, a geometric correction model was set up, converted into G-code, and validated using test prints for different wire parameters. For this, a sample of printed arcs was evaluated regarding wire position and embedding quality using various visual methods. This also determined the optimal cooling time for the model. The process parameters extrusion coefficient and feed were then varied to identify optimal process parameters for a stable and at the same time efficient process. By varying the wire (copper, constantan) and polymer material (PLA, PETG), the model was checked for general validity. It was found that the position of the ø 0.2 mm wire can be improved with the correction model. Different sets of parameters can be found that enable good quality of embedding and wire position.