Development and Control of a Flexible Actuation-Based Delta Robot

Delta robots are a popular type of robot used in industry for fast actuation whereas soft robotics is an emerging branch of robotics that aims to develop robots with flexible bodies. This research aims to develop a Delta Robot with flexible actuation to further the research carried out for soft robotic development. Most soft robots in literature utilize bending type actuators. The Reverse Pneumatic Artificial Muscle (RPAM) was used in this study as the type of flexible actuator which is ideal for extension-based applications which is necessary for Delta Robot-like behaviour. The RPAM was convenient to develop with latex rubber tubes and inextensible fiber wrappings in a double helical pattern. This configuration of fiber wrapping restricts radial expansion of the flexible tube and allows the actuator to have a high length to pressure increment ratio. Thereby, RPAMs provide a near linear relationship between pressure and strain as compared to other types of flexible actuators in literature. The robot developed in this study utilizes three RPAM actuators powered by compressed air. With such a configuration, the robot was expected to operate in a hemispherical working space. The robot developed achieved a hemispherical working space of radius 12.37cm and variation angle of 31°. PID control was used to regulate the pressure within the actuators. Through the actuation sequences of the solenoid valves, the robot end effector position was controlled with respect to the pressure of each actuator. Through the use of a Look-Up Table and interpolation, the robot can be commanded to move to the desired position in the working volume to successfully perform pick and place operations.