The surface Electromyography (sEMG) signal contains information about movement intention generated by the human brain, and it is the most intuitive and common solution to control robots, orthotics, prosthetics and rehabilitation equipment. In recent years, gesture decoding based on sEMG signals has received a lot of research attention. In this paper, the effects of muscle fatigue, forearm angle and acquisition time on the accuracy of gesture decoding were researched. Taking 11 static gestures as samples, four specific muscles (i.e., superficial flexor digitorum (SFD), flexor carpi ulnaris (FCU), extensor carpi radialis longus (ECRL) and finger extensor (FE)) were selected to sample sEMG signals. Root Mean Square (RMS), Waveform Length (WL), Zero Crossing (ZC) and Slope Sign Change (SSC) were chosen as signal eigenvalues; Linear Discriminant Analysis (LDA) and Probabilistic Neural Network (PNN) were used to construct classification models, and finally, the decoding accuracies of the classification models were obtained under different influencing elements. The experimental results showed that the decoding accuracy of the classification model decreased by an average of 7%, 10%, and 13% considering muscle fatigue, forearm angle and acquisition time, respectively. Furthermore, the acquisition time had the biggest impact on decoding accuracy, with a maximum reduction of nearly 20%.
This article, for the first time, presents the generation of Roots rotor tooth profiles based on an Assur-group-associated virtual linkage method. Taking the original Roots rotor as an example, structure and geometry of the Roots rotor are introduced, and based on the principle of inversion, an equivalent virtual linkage is identified for generating dedendum tooth profile of the rotor. Using linkage decomposition associated with elemental Assur groups, algorithm for computing the tooth curve is constructed leading to the explicit expression of rotor profile and the corresponding numerical simulation, verifying the validity of the proposed approach. For demonstration purpose, the virtual linkage method is then extended to the generation of tooth profiles for the variants of Roots rotors with arc-cycloidal curves and arc-involute curves. Integrated with computer-aided design, computer-aided engineering and computer-aided manufacturing software platforms, as well as the three-dimensional printing technology, this article provides an efficient and intuitive approach for Roots rotor system design, analysis and development.
PurposeThe purpose of this paper is to propose the situation that the existing parking automated guided vehicle (AGV) has a single walking mode, a spin forward motion mode based on a dual steering wheel driven parking AGV. In this way, the AGV can complete the 180° spin of the AGV in the process of straight forward.Design/methodology/approachA spin forward kinematics model of the dual steering wheel AGV is established, and a motion controller of the dual steering wheel AGV is designed based on the principle of model predictive control to complete the path following the spin forward motion mode.FindingsComputer simulations and laboratory tests were performed on this movement mode, which showed that the operation mode was feasible. It also verified that the mode can improve the handling efficiency, and also solved the problem that the parking space beside the wall could not be set and the site utilization was improved.Research limitations/implicationsThe controller should be further improved to make the operation smoother and more accurate.Practical implicationsThis mode has the applicability to the indoor logistics AGVs. In addition, it can improve the handling efficiency and also solved the problem that the storage space for goods beside the wall could not be set and the site utilization was improved.Social implicationsThis method can solve the problem due to the increasing number of private cars and parking spaces are hard to find. It increases the number of parking spaces and improves the utilization rate of the site. In addition, it also saves people the time to find a parking space and reduces car exhaust emissions in the process. It follows the requirements of sustainable development.Originality/valueThe studies in this paper provide AGV with more ideas on the issue of improving handling efficiency and site utilization and also solves the problem of being unable to set parking spaces when parking against the wall. In addition, this model has applicability to indoor logistics AGV and plays the same role.
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