Closed-loop Control of a Soft Robotic XY-table to Manipulate Delicate Objects

At present, soft robotic engineering is rapidly emerging as a significant part of the robotics. Recent research concerns a range of potential applications in terms of manipulating and transporting delicate work-pieces in the industrial production line. With the characteristics of soft materials, soft robots can bring a higher level of safety for human and operating objects during the interaction. Additionally, the flexible and soft structure of these robots allows them to adapt naturally to various environments without complicated control systems. Inspired by the caterpillar’s crawling gait, a particular kind of soft robot called a “soft table” has been proposed to solve applications in the bio-mimetic, medical and industrial field. This table is capable of translating and rotating objects on the top surface deriving from the deformation of its top surface. For constructing this deformation, an open-loop controller has been adopted to the soft table to produce surface movements in the current studies. Several studies have replicated this locomotion in their prototypes such as a novel soft machine table (Deng, Stommel & Xu, 2016) and other one developed at Auckland University of Technology (AUT) (Maratas, 2018). If Deng’s prototype has been consisted of a soft upper surface and rigid, non-moving sidewalls. Whereas, Maratas’s prototype achieves a more excellent working range by flexible sidewalls. The drawback of this fashion, however, is that the actuators bend unpredictably along their length. Additionally, operated by an open-loop control, the system does not sense the deformation of the actuators. In this study, these shortcomings are solved by integrating a sensor to measure the system state, and by enhancing either the stability or the flexibility of the soft sidewalls by origami techniques. The new soft XY-table proposed in this research study consists of an array of actuators, each of which is made by origami paper covered with a soft material. Origami folding paper technology from Japan has proved its ability related to high stiffness and broad elongation. Consequently, the soft origami actuator is capable of extending or contracting more widely along the vertical direction. This actuator hence not only expands its working range flexibly, but also creates a transformation on the top surface. Without rigid sidewalls, the proposed table is able to reduce the limitation of the movement amplitude on the top surface. Furthermore, an infrared sensor is embedded inside the actuator to control and monitor the robot’s operation. To validate the proposed methodology, several techniques have been applied with regards to constructing a system fashion, a pneumatic system, manufacturing of soft origami actuator, integrating the sensor, and calibrating the sensor as well. Working principle of the control system is based on inflating or deflating the air inside the actuator. It leads to an up and down movement of the actuator. A combination of these movements is to construct an object manipulation on top. A feedback signal from the sensor is necessary to monitor the operating state of the system. Our findings show that the working range of the new model is better than the previous one, and the sensors work correctly. In conclusion, this study manages to develop an entirely soft XY-table created from soft origami actuators, the pneumatic system and the feedback controller. This table offers potential applications in industrial and medical fields to handle fragile objects. Because of the modularity of the system, the soft actuators can be easily assembledin other designs apart from the table to meet the demands of further applications in healthcare, industrial automation, and food processing