The discrete element method (DEM) for modeling the behavior of particulate material is highly dependent on the use of appropriate and accurate parameters. In this study, a seed metering DEM simulation was used to measure, calibrate, and verify the physical and interactional parameters of rapeseed. The coefficients of restitution and static friction between rapeseeds and three common materials (aluminum alloy, acrylic, and high-density polyethylene) were measured using free drop and sliding ramp tests, respectively. The angle of repose was determined using a hollow cylinder experiment, which was duplicated using a DEM simulation, to examine the effects of static and rolling friction coefficients on the angle of repose. Response surface optimization was performed to determine the optimized model parameters using a Box–Behnken design test. A metering device was made with three materials, and rapeseed seeding was simulated at different working speeds to verify the calibrated parameters. The validation results showed that the relative errors between the seed metering model and experiments for the single qualified seeding, missed seeding, and multiple seeding rates were −0.15%, 3.29%, and 5.37%, respectively. The results suggest that the determined physical and interactional parameters of rapeseed can be used as references for future DEM simulations.

Flexible strain sensors based on liquid metal have great application potential in wearable devices, biomedicine and soft robots due to their huge deformability, low hysteresis and high durability. However, the existing fabrication method for the sensor faced with some challenges such as high cost, cumbersome process and long preparation time, which affect the development of the flexible sensors. Herein, this paper reported a flexible strain sensor based on liquid metal (FSS-LM) through atomizing spraying process. We optimized the spraying process, remarkably improving spraying quality. On the basis of the optimized spraying process, we quickly fabricated the FSS-LM with low cost. The sensor shows low hysteresis (1.18%), fast response (212ms), long durability (2000 stretching and releasing cycles), excellent dynamic and static performance, as well as good repeatability. Finally, the developed sensor was used to detect a variety of activities, including the bending of human joints and robot fingers, expansion of the balloon and the growth of plant stems. The results show that the FSS-LM exhibits great potential in the field of wearable devices.

Flexible three-dimensional (3D) force sensors have received extensive attention from researchers due to their characteristics of being able to detect both normal forces and tangential forces. However, most current flexible 3D force sensors still use metal electrodes, which have posed challenges such as low bending and stretching properties, easy fracture, and larger mass. Herein, this paper proposed a fully flexible 3D force sensor utilizing liquid metal directly as the electrode to achieve full flexibility. Besides, a dielectric layer with a porous pyramid array structure was adopted to improve the properties of the sensor. The influence of the square and triangular electrode shapes on the performance of sensor was verified through theoretical deductions and experiments. The results show that the triangular electrode sensor exhibits higher sensitivity. The maximum sensitivity of the triangular sensor in the normal +Z direction is , and the maximum sensitivities in the tangential +X and +Y directions are and , respectively. Moreover, the sensor possesses rapid response performance (143ms), low hysteresis (3.61%), high resolution, small temperature and humidity drift, satisfactory dynamic stability, and long-term stability. Finally, the sensor was installed on a manipulator for object grasping, verifying its ability to detect 3D forces and its potential in non-destructive grasping.