Soft Robotics in Transport Engineering

Abstract

This research explores the design and evaluation of the bio inspired soft robotic gripper for large object manipulation in the field of transport engineering. Bio-inspired soft robots use soft mechanical, structural or material components inspired from nature. The application of soft robotics can often be found on a small size scale but could also be beneficial on a larger size scale to manipulate larger objects and heavier objects. Manipulating large objects often requires many people working close to the object and gripper which can result in dangerous situations. Integrating soft robots can result in a improved safety during operation by preventing these accidents from happening. Also the flexible characteristics of these types of robots enables the manipulation of different types of objects. The main question this research answers is: What are the structural possibilities and limitations of bioinspired soft robots in break bulk manipulation? The objective of this research is to design and evaluate a
bio-inspired soft robot that is able to manipulate break bulk. The soft robotic gripper is designed by using the double diamond design method and by using different concept generation and evaluation tools. Generating concept designs is done using a morphological chart and selecting the concept is done using a modified Harris Profile. The most promising conceptual design is then selected and developed in more detail in the preliminary design. This design explores the different shapes and size using bio inspired design and drawing inspiration fromthe trunk of an elephant as gripper. This design is then modelled on a small size scale as well as the large size scale and evaluated using a FEA and MBD. After several iterations the detailed design could be created. The design of the gripper uses shape memory alloy (SMA) as actuators integrated in segments as building blocks to shape the gripper. The model of the single SMA spring is first designed and evaluated using a FEA program on a small size scale to compare with the physical spring on the same size scale. This model of the spring resembles the physical spring deviating 1.6% with the reaction force of 6.75 N on the simulation and 6.88 N on the physical spring. For the upscaled model this results in a reaction force of 255 N. The next step is to use this reaction force and apply it to the segment where the SMA spring is replaced with this force to obtain the segment bending angle. This results shows the bending angle of the segment of 29 degrees for the single SMA spring actuation and 80 degrees for the two spring actuation at 50% of the actuation force. At 100% of the actuation force, these bending angles increase up to 74 degrees and 126 degrees respectively. Using this result the range of motion (RoM) can be determined and compared with the prototype. This result presents a similar behaviour of the model with a slight decreased performance of the prototype over the simulations. The prototype of the single gripper can be combined with other grippers and work together to manipulate larger, heavier and more complex shaped objects. Combining three of these small size trunk inspired grippers shows the capability to lift an avocado of 276 grams or 2.7 N. Scaling this load capacity to the upscaled gripper shows the load capacity of 10.4 kg or 102 N. Improving the design and performing more research in the different types of objects regarding size, shape, weight and surface roughness can be done to increase this load capacity. This gripper design presented in this research can be seen as the initial step in the automation of large object manipulation. Possible applications of upscaling the gripper can be found in the area of construction sites, offshore industry and space exploration.