Experimental study of relationship between interfacial electroadhesive force and applied voltage for different substrate materials

An experimental investigation into the relationship between the interfacial electroadhesive force and applied voltage up to 20 kV has been presented. Normal electroadhesive forces have been obtained between a double-electrode electroadhesive pad and three optically flat and different substrate materials: glass, acrylic, and polycarbonate. The results have shown that not all substrate materials are good for the generation of electroadhesive forces. Only 15.7 Pa has been obtained between the pad and the polycarbonate substrate under 20 kV, whereas 46.3 Pa and 123.4 Pa have been obtained on the acrylic and glass substrate, respectively. Based on the experimental data, empirical models, with an adjusted R-square value above 0.995 in all cases, have been obtained for the three substrates. However, it has not been possible to develop a general empirical model which is suitable for all substrates. This further indicates the need for a large quantity of experimental data to obtain robust empirical models for different substrate materials in order to reliably use electroadhesive technologies for material handling applications

Symmetrical electroadhesives independent of different interfacial surface conditions

Current electroadhesive actuators cannot produce stable electroadhesive forces on the same substrate with different interfacial surface interactions. It is, therefore, desirable to develop electroadhesive actuators that can generate stable adhesive forces on different surface conditions. A symmetrical electroadhesive pad that is independent of different interfacial scratch directions is developed and presented. A relative difference of only 6.4% in the normal force direction was observed when the electroadhesive was facing an aluminium plate with surface scratch directions of 0°, 45°, 90°, and 135°. This step-change improvement may significantly promote the application of electroadhesion technology. In addition, this manifests that significant performance improvements could be achieved via further investigations into electroadhesive designs

Optimization and experimental verification of coplanar interdigital electroadhesives

A simplified and novel theoretical model for coplanar interdigital electroadhesives has been presented in this paper. The model has been verified based on a mechatronic and reconfigurable testing platform, and a repeatable testing procedure. The theoretical results have shown that, for interdigital electroadhesive pads to achieve the maximum electroadhesive forces on non-conductive substrates, there is an optimum electrode width/space between electrodes (width/space) ratio, approximately 1.8. On conductive substrates, however, the width/space ratio should be as large as possible. The 2D electrostatic simulation results have shown that, the optimum ratio is significantly affected by the existence of the air gap and substrate thickness variation. A novel analysis of the force between the electroadhesive pad and the substrate has highlighted the inappropriateness to derive the normal forces by the division of the measured shear forces and the friction coefficients. In addition, the electroadhesive forces obtained in a 5 d period in an ambient environment have highlighted the importance of controlling the environment when testing the pads to validate the models. Based on the confident experimental platform and procedure, the results obtained have validated the theoretical results. The results are useful insights for the investigation into environmentally stable and optimized electroadhesives

Toward adaptive and intelligent electroadhesives for robotic material handling

An autonomous, adaptive, and intelligent electroadhesive material handling system has been presented in this paper. The system has been proposed and defined based on the identification of a system need through a comprehensive literature review and laboratory-based experimental tests. The proof of the proposed concept has been implemented by a low cost and novel electroadhesive pad design and manufacture process, and a mechatronic and reconfigurable platform, where force, humidity, and capacitive sensors have been employed. This provides a solution to an autonomous elelctroadhesive material handling system that is environmentally and substrate material adaptive. The results have shown that the minimum voltage can be applied to robustly grasp different materials under different environment conditions. The proposed system is particularly useful for pick-and-place applications where various types of materials and changing environments exist such as robotic material handling applications in the textile and waste recycling industry

Geometric optimisation of electroadhesive actuators based on 3D electrostatic simulation and its experimental verification

A systematic research methodology for the performance evaluation of different electroadhesive pad geometries is demonstrated in this paper. The proposed research method for the investigation was based on a 3D electrostatic simulation using COMSOL Multiphysics, a cost-effective electroadhesive pad design and manufacturing process based on solid-ink printing, chemical etching, conformal coating, and an advanced and mechatronic electroadhesive force testing platform and procedure. The method has been validated using 2 novel pad designs, approximate 21 cm x 19 cm, compared with the normal comb design, on the glass and aluminium plate. The experimental results showed that: 1) on the glass substrate, a relative increase of 1% and 28% in the electroadhesive forces obtainable can be seen in the curve-comb pad and the worm-comb pad respectively; and 2) on the Al substrate, a relative increase of 5% and 12% can be seen. This manifests that the two new pad designs, especially the worm-comb shape design, are better at generating larger electroadhesive forces. The comparison between the simulation results and experimental results proved that proposed method is promising for evaluating the pad design before spending time and money on pad manufacture and testing

Investigation of relationship between interfacial electroadhesive force and surface texture

A novel investigation into the relationship between the obtainable interfacial electroadhesive forces and different surface textures is presented in this paper. Different surface textures were generated then characterized based on a recognized areal-based non-contact surface texture measurement platform and procedure. An advanced electroadhesive force measurement platform and procedure were then implemented to measure the obtainable electroadhesive forces on those different surface textures. The results show that the obtained interfacial electroadhesive forces increase with decreasing Sq (root mean square height) value of the substrate surface provided that the difference in Sq between the different substrates is over 5 μm. Also, the higher the applied voltage, the larger the relative increase in electroadhesive forces observed. However, when the difference of Sq value between different substrate surfaces is below 2 μm, the obtained interfacial electroadhesive forces do not necessarily increase with decreasing Sq. Furthermore, the obtainable electroadhesive forces are not necessarily the same when the Sq value of two substrate surfaces are the same due to the fact that the direction of the surface texture plays an important role in achieving electroadhesive forces

Visualization methods for understanding the dynamic electroadhesion phenomenon

Experimental investigation into the surface potential and electric field visualization of an electroadhesion system is presented for understanding the dynamic electroadhesion phenomenon. The indirect experimental approach has been based on measuring surface potentials on the surface of an electroadhesive pad by an electrostatic voltmeter. The direct approach has been based on charging and discharging the electroadhesive pad in a viscous oil mixed with lightweight particles. The visualization of the dynamic field distribution of electroadhesive pads can be a useful method to understand the dynamic electroadhesion phenomenon. In addition, indication of different field distributions of different pad geometries can be obtained through the method demonstrated here. Furthermore, the method is useful for instructors or lecturers to showcase or teach the dynamic electroadhesion phenomenon

Feasibility of detecting potential emergencies in symbiotic human-robot collaboration with a mobile EEG

Manufacturing challenges are driving the move from separated workspaces of either humans or robots towards a close, symbiotic collaboration. Symbiotic Human-Robot Collaboration requires both parties to not only share the same workspace, but to also perform tasks simultaneously. This raises questions of mutual awareness, for which safety is a critical factor. Despite advances regarding safety systems, human sensing abilities combined with the intelligence to anticipate potential emergencies cannot be matched. Subsequently, the human operator remains in a critical role regarding safety in Human-Robot Collaboration However, in a collaborative environment humans are expected to use their hands towards the completion of a task. Therefore, in order to achieve resilience for collaborative tasks, there is a need to have a hands free detection mechanism for unforeseen events. This work investigates a human sensor-based emergency stop interface that reacts once the human operator senses or anticipates a potential emergency. A novel approach is presented on how a mobile electroencephalogram (EEG) can be used to detect potential emergencies in Human-Robot Collaboration. An experiment was conducted with 21 participants, ten assembly tasks and three different kinds of potential emergencies. The potential emergencies included the collaborative robot to drop an assembly workpiece, to crush the assembly piece on the worktable, and to perform a simulated malfunction. The EEG data suggests strong similarities in the patterns between the different types of potential emergencies. High accuracies were be achieved with a Decision Tree Model based on Continuous Wavelet Transform peak counting. To optimize detection time, different detection window sizes were compared. The results showed a promising potential of this approach, which it is not intended to replace current safety systems but to enhance them towards a safer and thus symbiotic Collaboration

Toward Adaptive and Intelligent Electroadhesives for Robotic Material Handling

An autonomous, adaptive, and intelligent electroadhesive material handling system has been presented in this paper. The system has been proposed and defined based on the identification of a system need through a comprehensive literature review and laboratory-based experimental tests. The proof of the proposed concept has been implemented by a low cost and novel electroadhesive pad design and manufacture process, and a mechatronic and reconfigurable platform, where force, humidity, and capacitive sensors have been employed. This provides a solution to an autonomous elelctroadhesive material handling system that is environmentally and substrate material adaptive. The results have shown that the minimum voltage can be applied to robustly grasp different materials under different environment conditions. The proposed system is particularly useful for pick-and-place applications where various types of materials and changing environments exist such as robotic material handling applications in the textile and waste recycling industry

An adaptive human sensor framework for human-robot collaboration

Manufacturing challenges are increasing the demands for more agile and dexterous means of production. At the same time, these systems aim to maintain or even increase productivity. The challenges risen from these developments can be tackled through Human-Robot Collaboration (HRC). HRC requires effective task distribution according to each party’s distinctive strengths, which is envisioned to generate synergetic effects. To enable a seamless collaboration, the human and robot require a mutual awareness, which is challenging, due to the human and robot “speaking” different languages as in analogue and digital. This challenge can be addressed by equipping the robot with a model of the human. Despite a range of models being available, data-driven models of the human are still at an early stage. For this purpose, this paper proposes an adaptive human sensor framework, which incorporates objective, subjective, and physiological metrics, as well as associated Machine Learning. Thus, it is envisioned to adapt to the uniqueness and dynamic nature of human behavior. To test the framework, a validation experiment was performed, including 18 participants, which aims to predict Perceived Workload during two scenarios, namely a manual and an HRC assembly task. Perceived Workloads are described to have a substantial impact on a human operator’s task performance. Throughout the experiment physiological data from an electroencephalogram (EEG), an electrocardiogram (ECG), and respiration sensor was collected and interpreted. For subjective metrics, the standardized NASA Task Load Index was used. Objective metrics included task completion time and number of errors/assistance requests. Overall, the framework revealed a promising potential towards an adaptive behavior, which is ultimately envisioned to enable a more effective HRC.</div