An origami-based soft robotic actuator for upper gastrointestinal endoscopic applications

Soft pneumatic actuators have been explored for endoscopic applications, but challenges in fabricating complex geometry with desirable dimensions and compliance remain. The addition of an endoscopic camera or tool channel is generally not possible without significant change in the diameter of the actuator. Radial expansion and ballooning of actuator walls during bending is undesirable for endoscopic applications. The inclusion of strain limiting methods like, wound fibre, mesh, or multi-material molding have been explored, but the integration of these design approaches with endoscopic requirements drastically increases fabrication complexity, precluding reliable translation into functional endoscopes. For the first time in soft robotics, we present a multi-channel, single material elastomeric actuator with a fully corrugated design (inspired by origami); offering specific functionality for endoscopic applications. The features introduced in this design include i) fabrication of multi-channel monolithic structure of 8.5 mm diameter, ii) incorporation of the benefits of corrugated design in a single material (i.e., limited radial expansion and improved bending efficiency), iii) design scalability (length and diameter), and iv) incorporation of a central hollow channel for the inclusion of an endoscopic camera. Two variants of the actuator are fabricated which have different corrugated or origami length, i.e., 30 mm and 40 mm respectively). Each of the three actuator channels is evaluated under varying volumetric (0.5 mls-1 and 1.5 mls-1 feed rate) and pressurized control to achieve a similar bending profile with the maximum bending angle of 150°. With the intended use for single use upper gastrointestinal endoscopic application, it is desirable to have linear relationships between actuation and angular position in soft pneumatic actuators with high bending response at low pressures; this is where the origami actuator offers contribution. The soft pneumatic actuator has been demonstrated to achieve a maximum bending angle of 200° when integrated with manually driven endoscope. The simple 3-step fabrication technique produces a complex origami pattern in a soft robotic structure, which promotes low pressure bending through the opening of the corrugation while retaining a small diameter and a central lumen, required for successful endoscope integration

Simplifying Terrain Navigation with Soft Legs

Traditional robots, such as robotic arms in assembly lines, are designed for specialized, repeatable tasks. However, robotic applications are not always set in structured environments. Rather than using rigid components, soft robots made from soft materials are able to bend, extend, and deform. These movements enable soft robots to swim, walk, crawl, and grasp objects like the impressive capabilities of biological systems, such as the octopus. I hypothesized that the ability of soft legs to easily compress and bend would reduce the complexity of the control algorithms and hardware required for navigating unstructured obstacles. However, because soft walking robots move very differently than their rigid counterparts, they provide a new challenge. Soft appendages must be soft enough to passively adapt to the environment while being stiff enough to generate forces for walking.In this thesis, I have investigated methods to design, fabricate, model, and control soft-legged robots that are able to navigate over obstacles using simple control strategies. Inspired by nature, I found that a pneumatically actuated soft-legged quadruped robot with three actuated degrees-of-freedom (DoF) per leg was able to navigate over loose rocks or pebbles, squeeze into tight spaces, and walk underwater against flow when augmented with an inflatable soft body. I developed an application-driven design framework to relate the geometry and material properties of the soft legs to common metrics such as bend angle and blocked force. This design framework enables roboticists to rapidly design and fabricate soft robots to satisfy functional requirements. I also developed a lumped-parameter soft robot simulator to replicate the movement of the robot and used genetic algorithms to evolve practical, task-driven control strategies for accomplishing challenging problems, such as squeezing through a confined opening. Practical implementation of these gaits normally requires heavy and bulky pumps and valves which can be very challenging to carry onboard a robot with soft legs. To address this concern, I developed soft air-powered circuits to control the gait of the soft-legged robot without requiring any electronic components. The sequential behaviors were mechanically “programmed” in the circuit by storing information using the snap-through instability in hemispherical elastomeric membranes. The pneumatic memory elements in the circuits changed the walking direction of the robot based on physical interactions with the world. These pneumatic circuits could potentially be used to control electronics-free soft robots for navigating environments where electronics may not be suitable, such as environments sensitive to spark ignition. The contributions in this dissertation enable more versatile soft robotic systems which could potentially be used to monitor hazardous environments

Simplifying Terrain Navigation with Soft Legs

Traditional robots, such as robotic arms in assembly lines, are designed for specialized, repeatable tasks. However, robotic applications are not always set in structured environments. Rather than using rigid components, soft robots made from soft materials are able to bend, extend, and deform. These movements enable soft robots to swim, walk, crawl, and grasp objects like the impressive capabilities of biological systems, such as the octopus. I hypothesized that the ability of soft legs to easily compress and bend would reduce the complexity of the control algorithms and hardware required for navigating unstructured obstacles. However, because soft walking robots move very differently than their rigid counterparts, they provide a new challenge. Soft appendages must be soft enough to passively adapt to the environment while being stiff enough to generate forces for walking.In this thesis, I have investigated methods to design, fabricate, model, and control soft-legged robots that are able to navigate over obstacles using simple control strategies. Inspired by nature, I found that a pneumatically actuated soft-legged quadruped robot with three actuated degrees-of-freedom (DoF) per leg was able to navigate over loose rocks or pebbles, squeeze into tight spaces, and walk underwater against flow when augmented with an inflatable soft body. I developed an application-driven design framework to relate the geometry and material properties of the soft legs to common metrics such as bend angle and blocked force. This design framework enables roboticists to rapidly design and fabricate soft robots to satisfy functional requirements. I also developed a lumped-parameter soft robot simulator to replicate the movement of the robot and used genetic algorithms to evolve practical, task-driven control strategies for accomplishing challenging problems, such as squeezing through a confined opening. Practical implementation of these gaits normally requires heavy and bulky pumps and valves which can be very challenging to carry onboard a robot with soft legs. To address this concern, I developed soft air-powered circuits to control the gait of the soft-legged robot without requiring any electronic components. The sequential behaviors were mechanically “programmed” in the circuit by storing information using the snap-through instability in hemispherical elastomeric membranes. The pneumatic memory elements in the circuits changed the walking direction of the robot based on physical interactions with the world. These pneumatic circuits could potentially be used to control electronics-free soft robots for navigating environments where electronics may not be suitable, such as environments sensitive to spark ignition. The contributions in this dissertation enable more versatile soft robotic systems which could potentially be used to monitor hazardous environments

Design of a Screw Extruder for Additive Manufacturing

Our aim is to show that the screw extrusion process is comparable to current FDM 3D printing processes by implementing an innovative design along with an advanced control algorithm. A thermistor array was used to detect the temperature profile along the barrel during the extrusion process for feedback. This provided information in regards to the location of the melting point during extrusion. The current prototype was able to achieve open loop extrusion out of a 0.2mm diameter nozzle with a maximum output flow rate of 7.14 mm/second and retain a controlled temperature profile using bang-bang control throughout the extrusion proces