Fast Control of Negative Pressure Response of a Bio-inspired Suction Cup Actuated by Shape Memory Alloy

A bio-inspired suction cup actuated by shape memory alloy(SMA)for miniature wall climbing robots is developed based on studying characteristics of biological suction apparatus.Some fast control strategies are introduced to improve negative pressure response.Theoretic model of the suction cup is built,and simulation and experiments results indicate the effectiveness of the fast control strategies.The largest negative pressure of the suction cup can reach 14 000 Pa,and its generating and cancelling just need 5 s.Research results indicate the suction cup can be used as an adhesion mechanism for miniature wall climbing robots.

Suction Cup Samplers for Estimating Nitrate-Nitrogen in Soil Water in Irrigated Sugarbeet Production

Efforts have increased to measure nitrate losses from farmland under different management practices due to environmental and public concerns over levels of nitrate-nitrogen (NO3-N) in surface and ground waters. This study evaluated the effect of conventional tillage (CT) and strip tillage (ST) practices and three N application rates on NO3-N concentrations in soil water at a 76 cm depth under irrigated sugarbeet (Beta vulgaris L.) in a clay loam soil. Nitrogen rates were applied as dry urea at 120, 150, 180 kg N ha-1 in 2006;130, 160, 190 kg N ha-1 in 2007;and 110, 140, 170 kg N ha-1 in 2008. Soil water volumes were measured weekly during each growing season using three ceramic suction cup samplers per plot placed at a 76 cm depth below the soil surface under each tillage. Results indicated that NO3-N concentrations at the 76 cm depth in the soil profile were not significantly affected by either tillage practice or by N application rate due to soil variability across the field and due to suction cup samplers’ biased estimate of soil water. The three N rates under CT and ST practices maintained NO3-N concentrations below the root zone to levels exceeding the 10 mg L-1 safe drinking water maximum level in all three years. There were large variations in NO3-N concentrations among replicates within each tillage and N rate that were likely caused by variability in soil physical, hydraulic and chemical properties that impacted water movement through the soil profile, N dynamics and leaching below the root zone of sugarbeet. In conclusion, suction cup samplers are point water measurement devices that reveal considerable variability among replicates within each treatment due to the heterogeneity of field soils. Further, these samplers are not recommended in heterogeneous soils with preferential flow characteristics.

Modeling and Simulation of a Bonding Process for Space Solar Cells

A bonding process for space solar cells implemented by an automated coating and bonding system was theoretically investigated for future parametric studies to achieve better bonding quality. First, the mechanical properties of silicone adhesive and the vacuum suction cup were experimentally analyzed. Based on the constitutive relationship of four parts in the bonding process, the dynamic bonding process was modeled systematically, and numerically simulated by a commercial finite element analysis code, Adina. The final bonding edge-alignment error and the thickness and uniformity of the adhesive layer were obtained from simulation and validated by experiments. A simulation platform was created for predicting the final bonding quality via adjusting bonding parameters when dimensions of the solar cells and adhesive were changed.

A modular four-modal soft grasping device

It is a key challenge for soft grasping devices to stably grasp unstructured objects with multi-size and multi-shape. The conventional single-function grippers have some limitations in grasping the above kinds of objects. This work proposes a modular four-modal soft grasping device(MFSGD), which consists of soft fingers, suction cups, soft wrapper, and other structures. It can perform a variety of grasping modes such as bending grasping mode, wrapping grasping mode, end liftingsucking mode, and side fixed-sucking mode. It may be one of the devices with the most grasping modes at present. Moreover, the device adopts a fully modular design with different structures connected by magnets. It is not only convenient to disassemble or assemble, so as to solve the mutual interference of different modal structures problem during grasping, but also simplifies the fabrication of the multi-modal grasping device. In addition, this work matches the suitable grasping modes for objects of different shapes and sizes, and obtains the relative characteristics of the MFSGD. The proposed device can improve the ability of the grasping robots, and is expected to play an important role in economic and industrial fields.