19 October 2018 in IEEE Transactions on Robotics
Nowadays, the most adopted model for the design and control of soft robots is the piecewise constant curvature model, with its consolidated benefits and drawbacks. In this work, an alternative model for multisection soft manipulator dynamics is presented based on a discrete Cosserat approach, in which the continuous Cosserat model is discretized by assuming a piecewise constant strain along the soft arm. As a consequence, the soft manipulator state is described by a finite set of constant strains. This approach has several advantages with respect to the existing models. First, it takes into account shear and torsional deformations, which are both essential to cope with out-of-plane external loads. Furthermore, it inherits desirable geometrical and mechanical properties of the continuous Cosserat model, such as intrinsic parameterization and greater generality. Finally, this approach allows to extend to soft manipulators, the recursive composite-rigid-body and articulated-body algorithms, whose performances are compared through a cantilever beam simulation. The soundness of the model is demonstrated through extensive simulation and experimental results.
22 April 2014 in Unmanned Systems
1 June 2007 in The International Journal of Robotics Research
In this paper we present a tutorial introduction to two important senses for biological and robotic systems — inertial and visual perception. We discuss the fundamentals of these two sensing modalities from a biological and an engineering perspective. Digital camera chips and micro-machined accelerometers and gyroscopes are now commodities, and when combined with today's available computing can provide robust estimates of self-motion as well 3D scene structure, without external infrastructure. We discuss the complementarity of these sensors, describe some fundamental approaches to fusing their outputs and survey the field.
1 June 2007 in The International Journal of Robotics Research
This paper proposes an approach to calibrate off-the-shelf cameras and inertial sensors to have a useful integrated system to be used in static and dynamic situations. When both sensors are integrated in a system their relative pose needs to be determined. The rotation between the camera and the inertial sensor can be estimated, concurrently with camera calibration, by having both sensors observe the vertical direction in several poses. The camera relies on a vertical chequered planar target and the inertial sensor on gravity to obtain a vertical reference. Depending on the setup and system motion, the translation between the two sensors can also be important. Using a simple passive turntable and static images, the translation can be estimated. The system needs to be placed in several poses and adjusted to turn about the inertial sensor centre, so that the lever arm to the camera can be determined. Simulation and real data results are presented to show the validity and simple requirements of the proposed methods.