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Because the motor and reducer of the conventional tandem welding robot are installed at the revolute joint, the robot has large rotational inertia and long residual vibration time. However, due to the limitation of workspace and other reasons, the current parallel robot is not suitable for all series welding robots. Therefore, based on the concept of "multi-degree-of-freedom controllable mechanism", a new controllable mechanism welding robot is proposed in this paper. The driving motor and reducer, which have great influence on the main and branch chain of the welding robot, are installed on the frame. The advantage of this design is that the inertia of the robot mechanism is significantly reduced, and its dynamic performance is improved. The position errors of the end members of the welding robot moving along the circle, as well as the angle errors of each joints under the circle movements are analysed.

Compliance control is one way to achieve compliance for rigid robots and is widely used in cooperative robots, lightweight robots, and exoskeleton robots. Real-time accurate collection of joint torque data is essential for compliance control during dynamic physical interactions with humans or the environment. Therefore, it is highly desirable to develop high-frequency joint torque sensor (JTS) that are accurate and sensitive and that can be properly calibrated. Toward this end, we propose herein a multi-objective optimization design method to improve the elastic strain distribution in the strain gauge working area, thereby improving the sensitivity of JTS. An analysis and comparison of a variety of easily manufactured inner hole spoke structures shows that the circle-rhombus type spoke structure is the most sensitive. An amplifier and low-pass filter circuit are designed for signal acquisition. An analysis of the sensitivity, linearity, hysteresis, repeatability, resolution, zero drift, and mechanical response of the sensor shows that the optimal sensor designed with high sensitivity of 30.5 mV/Nm, ±100 Nm capacity, 0.1 Nm resolution and 78.8 g weight, and the sampling frequency is 2 kHz. The experimental results show that the JTS is lightweight with high sensitivity and resolution, low noise, high dynamic response, all of which satisfy the design requirements. These results lead to an efficient and economical method of customizing JTS. [ABSTRACT FROM AUTHOR]

Among the shortcomings of the A* algorithm, for example, there are many search nodes in path planning, and the calculation time is long. This article proposes a three-neighbor search A* algorithm combined with artificial potential fields to optimize the path planning problem of mobile robots. The algorithm integrates and improves the partial artificial potential field and the A* algorithm to address irregular obstacles in the forward direction. The artificial potential field guides the mobile robot to move forward quickly. The A* algorithm of the three-neighbor search method performs accurate obstacle avoidance. The current pose vector of the mobile robot is constructed during obstacle avoidance, the search range is narrowed to less than three neighbors, and repeated searches are avoided. In the matrix laboratory environment, grid maps with different obstacle ratios are compared with the A* algorithm. The experimental results show that the proposed improved algorithm avoids concave obstacle traps and shortens the path length, thus reducing the search time and the number of search nodes. The average path length is shortened by 5.58%, the path search time is shortened by 77.05%, and the number of path nodes is reduced by 88.85%. The experimental results fully show that the improved A* algorithm is effective and feasible and can provide optimal results. [ABSTRACT FROM AUTHOR]

Most driving torques in serial industrial robots are used to overcome the weight of the robot. Although actuators account for a large proportion of the total mass of a robot, they have yet to become a positive factor that enables the robot to achieve gravity balance. This study presents a host–parasite structure to reconstruct the distribution of actuators and achieve gravity balance in robots. First, based on the characteristics of tree–rattan mechanisms, a method for calculating the degrees of freedom and a symbolic representation method for the distribution of branched chains are formulated for host–parasite mechanisms. Second, a configuration analysis and optimization method for host–parasite structure-based robots and a robot prototype are presented. Finally, four host–parasite mechanisms/robots (A, B, C, and D) are compared. The results are as follows. If more parasitic branched chains are added to the yz plane, the loads along axes 2 and 3 become more balanced, which significantly increases the stiffnesses of the mechanism in the y - and z -directions (Ky and Kz, respectively). If the additional branched chains are closer to the site of maximum deformation, the stiffness of the mechanism in the z -direction (Kz) increases more significantly. Of the four mechanisms, mechanism D has the best overall performance. The joint torques of mechanism D along axes 2 and 3 are lower than those of mechanism A by 99.78% and 99.18%, respectively. In addition, Kx, Ky, and Kz of mechanism D are 100.56%, 336.19%, and 385.02% of those of mechanism A, respectively. Moreover, the first-order natural frequency of mechanism D is 135.94% of that of mechanism A. Host–parasitic structure is conducive to improving the performance of industrial robots. [ABSTRACT FROM AUTHOR]