Origami-Inspired Printed Robots

Robot manufacturing is currently highly specialized, time consuming, and expensive, limiting accessibility and customization. Existing rapid prototyping techniques (e.g., 3-D printing) can achieve complex geometries and are becoming increasingly accessible; however, they are limited to one or two materials and cannot seamlessly integrate active components. We propose an alternative approach called printable robots that takes advantage of available planar fabrication methods to create integrated electromechanical laminates that are subsequently folded into functional 3-D machines employing origami-inspired techniques. We designed, fabricated, and tested prototype origami robots to address the canonical robotics challenges of mobility and manipulation, and subsequently combined these designs to generate a new, multifunctional machine. The speed of the design and manufacturing process as well as the ease of composing designs create a new paradigm in robotic development, which has the promise to democratize access to customized robots for industrial, home, and educational use.National Science Foundation (U.S.). Expeditions Program (Grant CCF-1138967

Towards Agility: Definition, Benchmark and Design Considerations for Small, Quadrupedal Robots

Agile quadrupedal locomotion in animals and robots is yet to be fully understood, quantified or achieved. An intuitive notion of agility exists, but neither a concise definition nor a common benchmark can be found. Further, it is unclear, what minimal level of mechatronic complexity is needed for this particular aspect of locomotion. In this thesis we address and partially answer two primary questions: (Q1) What is agile legged locomotion (agility) and how can wemeasure it? (Q2) How can wemake agile legged locomotion with a robot a reality? To answer our first question, we define agility for robot and animal alike, building a common ground for this particular component of locomotion and introduce quantitative measures to enhance robot evaluation and comparison. The definition is based on and inspired by features of agility observed in nature, sports, and suggested in robotics related publications. Using the results of this observational and literature review, we build a novel and extendable benchmark of thirteen different tasks that implement our vision of quantitatively classifying agility. All scores are calculated from simple measures, such as time, distance, angles and characteristic geometric values for robot scaling. We normalize all unit-less scores to reach comparability between different systems. An initial implementation with available robots and real agility-dogs as baseline finalize our effort of answering the first question. Bio-inspired designs introducing and benefiting from morphological aspects present in nature allowed the generation of fast, robust and energy efficient locomotion. We use engineering tools and interdisciplinary knowledge transferred from biology to build low-cost robots able to achieve a certain level of agility and as a result of this addressing our second question. This iterative process led to a series of robots from Lynx over Cheetah-Cub-S, Cheetah-Cub-AL, and Oncilla to Serval, a compliant robot with actuated spine, high range of motion in all joints. Serval presents a high level of mobility at medium speeds. With many successfully implemented skills, using a basic kinematics-duplication from dogs (copying the foot-trajectories of real animals and replaying themotion on the robot using a mathematical interpretation), we found strengths to emphasize, weaknesses to correct and made Serval ready for future attempts to achieve even more agile locomotion. We calculated Servalâs agility scores with the result of it performing better than any of its predecessors. Our small, safe and low-cost robot is able to execute up to 6 agility tasks out of 13 with the potential to reachmore after extended development. Concluding, we like to mention that Serval is able to cope with step-downs, smooth, bumpy terrain and falling orthogonally to the ground

Soft actuator and agile soft robot

Robots play an important part in many aspects of our society by doing repetitive, dangerous, or precision tasks. Most existing robots are made of rigid components, which lack passive compliance and pose a challenge in adapting to the environment and safe human-robot interaction. Rigid robots may be equipped with sensors and programmed with proprioceptive feedback control to achieve active compliance, but this may fail in the event of unforeseen situations or sensor failure. In contrast, animals have evolved flexible or soft body parts to help them adapt to changing environments. Soft robotics is an emerging field in robotics, drawing inspiration from nature by integrating soft material into the actuator and mechanical design. With the inclusion of soft material, soft actuators and robots can deform actively/passively, making it possible to sense, absorb impact, and adapt to its environment with deformation. However, while soft actuators/robots have superior properties to rigid ones, they are often challenging to manufacture and control precisely. In addition, they may suffer from slow speed and material degradation. Thus, in this thesis, we aim to address the issues in developing high-performance soft actuators and soft robots. The thesis is divided into two parts. In the first part, we focus on improving the manufacturability and performance of a self-contained soft actuator originated in the Creative Machines Lab. The soft actuator is composed of a cured silicone-ethanol mixture embedded with heating coils. When the coils are electrically actuated, ethanol trapped inside undergoes liquid-vapor transitions, and thus the actuator undergoes extreme volume change. While this actuator exhibits high strain and high stress, it is very slow to actuate, has limited life cycles, and requires molds to manufacture. The first part of the thesis will address these issues. Specifically, in chapter 2, we discuss using multi-material 3D printing to automate the manufacturing of silicone-ethanol composite. In chapter 3, we discuss using laser-cut flexible Kirigami patterns to improve the manufacturability of its heating element. Chapter 4 characterizes its actuation profile and addresses improvements to the thermal conductivity by infusing thermally conductive fillers. Soft actuation is an actively researched area; however, many high-performance soft actuators are challenging to manufacture and thus are less accessible to the general robotics community. Conventional actuators such as electric motors are widely available but lack flexibility. Therefore, the second part of the thesis aims at combining rigid motors with soft materials to design and control high-performance hybrid soft robots. Simulation is a good way to evaluate and optimize robot design and control. However, existing simulators that support motor-driven soft robots have limited features. Chapter 5 discusses this issue and presents a physically based real-time soft robot simulator capable of simulating motor-driven soft robots. In addition, chapter 5 presents the design and control of a 3D printed hybrid soft quadruped robot. Chapter 6 presents the design and control of a 3D printed hybrid soft humanoid robot. The two parts of the thesis aim to improve aspects in soft actuators and soft robots. In conclusion, we summarize the lessons learned in developing soft actuators/robots and new possibilities and challenges for advancing soft robotics research

Biomimetic leg design and passive dynamics of Dolomedes aquaticus

Spiders provide working models for agile, efficient miniature passive-dynamic robots. Joints are extended by haemoplymph (hydraulic) pressure and flexed by muscle-tendon systems. Muscle contraction in the prosoma leads to an increase in hydraulic pressure and subsequently leg extension. Analysis of body kinematics the New Zealand fishing spider, Dolomedes aquaticus indicates that elastic plates around the joints absorb energy from the ground reaction force when the force vector points backwards (i.e. would decelerate the spider’s body in the direction of locomotion) and release it to provide forward thrust as the leg swings backwards. In addition to improving energy efficiency, this mechanism improves stability by passively absorbing energy from unpredictable foot-ground impacts during locomotion on uneven terrain. These principles guided an iterative design methodology using a combination of 3D modelling software and 3D printing techniques. I compared and contrasted compliant joints made of a variety of plastic materials. The final 3D-printed spider leg prototype has a stiff ABS exoskeleton joined by a compliant polypropylene backbone. The entire structure envelopes a soft silicone pneumatic bladder. FEA analysis was used to determine the ideal shape and behavior of the pneumatic bladder to actuate the exoskeleton. The spider leg can be flexed and contracted depending on the input pressure. To laterally actuate this pneumatic spider leg I designed and developed a fabrication system that uses vacuum injection molding to produce an integrated mesh sleeve/elastomer pneumatic actuator. I designed an apparatus to measure pressure and contraction of silicone and latex pneumatic muscles when inflated. I analyzed the non-linear pressure-contraction relationships of silicone versus latex pneumatic muscles, and also derived force-contraction relationships. From efficiency studies, both media muscles proved to be inefficient and the measuring apparatus needs to be more robust to prevent leaking air. The fabrication process still offers the possibility of a quick and efficient method of creating pneumatic muscles. A spider-like robot that implements these pneumatic muscles and pneumatic leg design could be used to explore the efficiency and stability of passive dynamic legged locomotion in spider-like robots

Control Implementation of Dynamic Locomotion on Compliant, Underactuated, Force-Controlled Legged Robots with Non-Anthropomorphic Design

The control of locomotion on legged robots traditionally involves a robot that takes a standard legged form, such as the anthropomorphic humanoid, the dog-like quadruped, or the bird-like biped. Additionally, these systems will often be actuated with position-controlled servos or series-elastic actuators that are connected through rigid links. This work investigates the control implementation of dynamic, force-controlled locomotion on a family of legged systems that significantly deviate from these classic paradigms by incorporating modern, state-of-the-art proprioceptive actuators on uniquely configured compliant legs that do not closely resemble those found in nature. The results of this work can be used to better inform how to implement controllers on legged systems without stiff, position-controlled actuators, and also provide insight on how intelligently designed mechanical features can potentially simplify the control of complex, nonlinear dynamical systems like legged robots. To this end, this work presents the approach to control for a family of non-anthropomorphic bipedal robotic systems which are developed both in simulation and with physical hardware. The first is the Non-Anthropomorphic Biped, Version 1 (NABi-1) that features position-controlled joints along with a compliant foot element on a minimally actuated leg, and is controlled using simple open-loop trajectories based on the Zero Moment Point. The second system is the second version of the non-anthropomorphic biped (NABi-2) which utilizes the proprioceptive Back-drivable Electromagnetic Actuator for Robotics (BEAR) modules for actuation and fully realizes feedback-based force controlled locomotion. These systems are used to highlight both the strengths and weaknesses of utilizing proprioceptive actuation in systems, and suggest the tradeoffs that are made when using force control for dynamic locomotion. These systems also present case studies for different approaches to system design when it comes to bipedal legged robots

An Energy Efficient Electro-Hydraulic Control System For A Collaborative Humanoid Robot

DissertationThis study presents the design of an energy efficient electro-hydraulic control system for a collaborative humanoid robot. Robots can be found in almost every aspect of our lives with different applications such as manufacturing, construction, agriculture, surgery, and transportation. The need for robots is on the rise as they perform certain tasks much faster and with more precision than humans. The lack of them having cognitive ability limits them in certain tasks as human interaction is often needed. Humans are currently better than robots in performing some tasks such as decision making and problem solving. In collaborative robotics, humans and robots are required to work together to achieve a common goal. In most cases, this is achieved by confining both entities in the same space. This allows for better accuracy for these robots with the flexibility and cognition of humans. Furthermore, research lately shows an increase in robots that use hydraulics with most showing that these hydraulics have energy saving abilities in robotic actuation. It is known that hydraulics have a high power to weight ratio thus allowing for more powerful yet compact robots to be built. An electro-hydraulic control system is thus described in this research in which the system allows the human user to manipulate the robot by having it mimic the user’s moves. This approach allows the user to not do any strenuous activities while the robot does the heavy lifting. Furthermore, the system does not need to be reprogrammed for a new task therefore reducing the reconfiguration time of the system. The proposed approach further allows the robot to work in hazardous situations while the user is in a safe environment. The system uses a proportional-integral-derivative (PID) algorithm to control a hydraulic cylinder allowing it to move with the user. Experiments performed to validate the study shows the reaction time as well as energy saving abilities of the system. Additionally, the results show that hydraulic systems have the ability to save energy during stall as well as increasing power density of the robot. Furthermore, an improved response time was recorded for the hydraulic system when being controlled by a remote operator

Kinematics analysis of a FLHL robot parallel-executed cylinder mechanical integration system with force/position hybrid control servo actuator

In this research subtopic, an electro-hydraulic servo four-legged heavy load (FLHL) robot has been designed and developed. This paper proposes an integration layout cylinder design scheme for a non-lightweight hydraulic servo four-legged robot with high loads and torques of hip joint, and derives the mathematical element analysis model for a parallel hydraulic servo cylinder system. The multiple inherent characteristics of the parallel-executed cylinder integration system model are further explored. Based on the controllable functional requirements of interconnected joints and weakening the influence of internal force coupling, a design idea of force/position hybrid control scheme for the parallel-executed cylinder is determined, and then the force/position signal module design unit is used to reversely solve the force/position hybrid control. Considering the inherent requirements of the servo-executed cylinder force control unit module, the implementation process of magnetic flux compensation and speed compensation is discussed in detail. The minimum amplitude controller is applied to the servo-executed cylinder force unit module, and the proportional integrated controller has been determined in the servo-executed cylinder position control unit module. A compound control strategy proposed in this paper is verified on a parallel hydraulic servo platform. The experimental verification results reveal that the values of position/force attenuation amplitude and lag phase are not greater than 9 % and 18°, respectively. In addition, the feasibility of the interconnected implementation of the hybrid control scheme proposed in this paper is further deepened. The effective conclusion of this research will be accepted in the application field of FLHL robot control system