ON THE ACCURACY OF POSITIONING OF MOBILE ROBOT'S WALKING PROPULSION DEVICES

The problems of the influence of the choice of the kinematic scheme of the walking mechanism on the positioning accuracy of its foot with the same small positioning errors are considered. The relationships between the laws of changing the coordinates of the foot of the walking mechanism as a material point and the change in the position of the output elements of the motors of the drives of the orthogonal mover and the mover with a parallel chain of drives are established.

Design of a 4-DoF (degree of freedom) hybrid-haptic device for laparoscopic surgery

This paper presents a novel kinematics architecture with 4 DoFs (degrees of freedom) intended to be used as a haptic interface for laparoscopic surgery. The proposed architecture is a result of an association of serial and parallel kinematics chains, with each one handling a part of the whole device DoF. The serial chain allows one to handle the translation and self-rotation and the parallel chain handles the two tilt motions, and this in a disjoint way as the natural gesture of the surgeon. The proposed hybrid-haptic device (HH device) benefits from the split DoF to ensure a good kinematic performance, large workspace, as well as gravity compensation. The kinematics study of the HH device is presented and followed by the optimal dimensional synthesis and the gravity compensation model.

Poplar flower-like nitrogen-doped carbon nanotube@VS4 composites with excellent sodium storage performance

As a new anode material for sodium-ion batteries (SIBs), VS4 shows impressive energy storage potential due to its unique one-dimensional parallel chain structure, large chain spacing and high sulfur content.

Spare Pose Graph Decomposition and Optimization for SLAM

The graph optimization has become the mainstream technology to solve the problems of SLAM (simultaneous localization and mapping). The pose graph in the graph based SLAM is consisted with a series of nodes and edges that connect the adjacent or related poses. With the widespread use of mobile robots, the scale of pose graph has rapidly increased. Therefore, optimizing a large-scale pose graph is the bottleneck of application of graph based SLAM. In this paper, we propose an optimization method basing on the decomposition of pose graph, of which we have noticed the sparsity. With the extraction of the Single-chain and the Parallel-chain, the pose graph is decomposed into many small subgraphs. Compared with directly processing the original graph, the speed of calculation is accelerated by separately optimizing the subgraph, which is because the computational complexity is increasing exponentially with the increase of the graph’s scale. This method we proposed is very suitable for the current multi-threaded framework adopted in the mainstream SLAM, which separately calculate the subgraph decomposed by our method, rather than the original optimization requiring a large block of time in once may cause CPU obstruction. At the end of the paper, our algorithm is validated with the open source dataset of the mobile robot, of which the result illustrates our algorithm can reduce the one-time resource consumption and the time consumption of the calculation with the same map-constructing accuracy.

Crystal structure of a twisted-ribbon type double-stranded AgIcoordination polymer:catena-poly[[silver(I)-μ3-bis(pyridin-3-ylmethyl)sulfane-κ3N:N′:S] nitrate]

The asymmetric unit in the title compound, {[Ag(C12H12N2S)]·NO3}nor {[AgL]·NO3}n,L= bis(pyridin-3-ylmethyl)sulfane, consists of an AgIcation bound to a pyridine N atom of anLligand and an NO3−anion that is disordered over two orientations in an 0.570 (17):0.430 (17) occupancy ratio. Each AgIcation is coordinated by two pyridine N atoms from adjacentLligands to form an infinite zigzag chain along [110]. In addition, each AgIion binds to an S donor from a thirdLligand in an adjacent parallel chain, resulting in the formation of a twisted-ribbon type of double-stranded chain propagating along the [110] or [1-10] directions. The AgIatom is displaced out of the trigonal N2S coordination plane by 0.371 (3) Å because of interactions between the AgIcation and O atoms of the disordered nitrate anions. Intermolecular π–π stacking interactions [centroid-to-centroid distance = 3.824 (3) Å] occur between one pair of corresponding pyridine rings in the double-stranded chain. In the crystal, the double-stranded chains are alternately stacked along thecaxis with alternate stacks linked by intermolecular π–π stacking interactions [centroid-to-centroid distance = 3.849 (3) Å], generating a three-dimensional supramolecular architecture. Weak intermolecular C—H...O hydrogen bonds between the polymer chains and the O atoms of the nitrate anions also occur.

An Adjustable Single Degree-of-Freedom System to Guide Natural Walking Movement for Rehabilitation

This paper presents a linkage system designed to guide a natural ankle trajectory with the corresponding foot orientation. A six-bar linkage was designed to coordinate the joint angles of an RR chain (R denotes a revolute or hinged joint) that models the leg to achieve the desired ankle trajectory. The design is shown to be adjustable to meet a range of trajectories obtained in an individual's normal gait. Control of the foot position is obtained using a cam-driven parallel chain that has the same input as the six-bar linkage. The design of the linkage was carried out using linkage synthesis theory and optimization methods. The result is a one degree-of-freedom system that guides a natural walking movement of the leg and foot. A solid model of the complete device is presented. The results of this research provide a procedure that focuses on the kinematics and mechanical design of a device named the UCI gait mechanism.