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For the computation of rigid body dynamics, the Newton-Euler equations represent a crucial relation unifying the laws of motion by Newton and Euler using the language of instantaneous screws. Typically, Newton-Euler equations are stated in spatial or in body coordinates, respectively. In this paper, a general formulation of Newton-Euler equations is provided for arbitrary reference systems. In particular, the general form unifies the known equations in spatial and body coordinates. To the best of the authors' knowledge, this relation between the spatial and the body form has not been reported in literature. The novel formulation is based on the concept of time differentiation with respect to moving reference systems.

In this article, a novel characterization of the workspace of 3R chains with non-orthogonal, intersecting axes is derived by describing the set of singular orientations as two tori that separate two-solvable from non-solvable orientations within SO(3). Therefore, the tori provide the boundary of the workspace of the axes' constellation. The derived characterization generalizes a recent result obtained by Piovan and Bullo. It is based on a specific, novel representation of rotations, called unit ball representation, which allows to interpret the workspace characterization with ease. In an appendix, tools for dealing with angles and rotations are introduced and the equivalence of unit quaternion representation and unit ball representation is described.

This paper presents the methodology followed on the design of a multi-contact point haptic interface that uses a bio-inspired control approach and a novel actuation system. The combination of these components aims at creating a system that increases the operability of the target, and, at the same time, enables an intuitive and safe tele-operation of any complex robotic system of any given morphology. The novelty lies on the combination of a thoughtful kinematic structure driven by an active-compliant actuation system and a bio-inspired paradigm for its regulation. Due to the proposed actuation approach, the final system will achieve the condition of wearable system. On that final solution, each joint will be able to change its stiffness depending on the task to be executed, and on the anatomical features of each individual. Moreover, the system provides a variety of safety mechanisms at different levels to prevent causing any harm to the operator. In future, the system should allow the complete virtual immersion of the user within the working scenario.