Inputting text is a fundamental task users perform in immersive virtual reality (VR) environments. This preliminary study quantifies the ‘gorilla arm’ effect regarding the required torque in the upper limb joints of an individual during a VR text entry task via ray-casting. This type of fatigue can be caused by the weight of the users’ arms, depending on the arm pose maintained during a task. We used motion capture technology to compare the required arm joints’ torque in two typical arm poses during VR text entry tasks. The results suggest that extending the arm higher and in front of the body towards the virtual keyboard causes about 3.77 times more net torque on the shoulder joint and 2.00 times more on the elbow joint, compared to when the arm is in a more relaxed and lowered position. These findings can support future VR text entry studies concerned with physical ergonomics.

This paper describes a kind of mobile robot, named cable-climbing robot, and its motion planning development. That robotic system is capable of moving over electricity distribution lines, which can easily overcome the obstacles present in those installations like insulators, thanks to its kinematic motion planning of collision avoidance. The cable-climbing robot avoids the obstacles by the adoption of sequential movement planning with the objective of climbing insulators in electric posts. This approach avoids the obstacles, making the robot-articulated suspensions to retract when it is close to the obstacle and to distend after it passes over it. This kind of movement is controlled by a geometric motion planning method which is performed by the quintic polynomial interpolation law. The kinematic modelling uses the screw-based Jacobian Method combining with Virtual Kinematic chains, which permits the usage of the Kirchhoff-Davies method. Thus obtaining the cable-climbing robot inverse kinematic model. Simulation shows the potential use of this technique to cope with the cable-climbing robots control.

This paper aims to explore mechanisms that allow the establishment of a sustainable basis between designers and craftsmen in the context of their joint collaboration, to enable the revitalization and upgrading of the craft manufacturing processes through technological resources and concepts implemented in the industry focused on CAX (Computer Aided Technologies). The objective is to contribute to the project development and to its previous analysis before starting the production. In this regard, pilot projects have been developed between designers of the Design course of the University of Madeira and students of the Craft course in wicker, specialized in furniture, promoted and taught by IVBAM (Wine Embroidery and Crafts Institute, Madeira). This project attempts to address new development strategies through the application of design methodologies and the use of CAD (Computer Aided Design) technology in the craft manufacturing process, aiming at optimising processes and at providing craftsman with resources that allow them to upgrade and improve their production systems

Reduced workspace is the main parallel robot disadvantage. It is generally due to the robot configuration, mainly the platform orientation constraint, the present work intends to find the maximum sphere within the orientation workspace, i.e., the singularity-free orientation regions. These regions are related to the platform orientation through Roll-Pitch-Yaw angles. Therefore, an optimization genetic algorithm is used to determine the initial platform orientation corresponding to the largest sphere volume. In this algorithm, the geometrical parameters and the direct and inverse singularities are the optimization constraints. The geometrical constraints may be studied using vectorial analysis. The reciprocity property from screw theory is implemented to analyze the direct and inverse kinematic. In this work it is used a methodology to verify the singularity closeness measure associated with direct kinematic. This measure is related to the rate of work done by each leg upon the platform twist. To determine how close is the parallel robot to a direct singularity a index value is proposed. It is considered that the passive joints reachable regions may be limited by a cone, whereby the cone symmetric axis is the same than the passive joint axis. In the optimization problem, the sphere volume, i.e., the maximal angular displacement of the moving platform around any axis is the objective function. Thus, the genetic algorithm individuals explore all feasible regions looking for an optimal solution.

Multi-phase flow, characterised by the presence of both liquid and gas phases, often occurs in riser pipes during oil extraction. These flows can be problematic because they can cause oscillations due to the formation of bubbles within the pipes, which can negatively impact the safety and efficiency of offshore production operations. One solution to this problem is to use a gravitational oil separator, which is designed to dampen these oscillations. The separator is equipped with a control system that uses liquid level and gas pressure sensors to stabilise the flow by adjusting the positions of its valves. This paper presents the use of a specific type of model-based predictive controller to control the level and pressure of a biphasic oil separator, particularly in the presence of slug disturbances. The designs of the separator model and controller are discussed in detail, with a focus on the advantages of using an unrestricted horizon predictive controller, such as its ability to make predictions over a long horizon and its relatively low computational requirements. For the sake of comparison, a linear quadratic regulator is also evaluated. The simulation results demonstrate that the proposed control system is able to effectively regulate the separator’s liquid level and gas pressure within a magnitude range of ${10}^{-4}$ m for the liquid level and ${10}^{-3}$ bar for the internal pressure. Aside from that, the dynamics of the closed-loop system is six times faster than the plant’s for the liquid behaviour and 30 times faster for the pressure, while also presenting sharp attenuation characteristics for the input disturbances of nearly 50 dB for the pressure output and 68 dB for the liquid level.