271 research outputs found
TinyTerp: A FULLY AUTONOMOUS MOBILE SMART CENTI-ROBOT
A fully autonomous modular 8 cm3 robot is presented using commercially available off-the-shelf (COTS) components. The robot introduced is called Tiny Terrestrial Robotic Platform (TinyTeRP) which provides an inexpensive, easily assembled, small robotic platform for researchers to study swarm behavior. TinyTeRP can be assembled in 30 minutes and costs $51.50. TinyTeRP is fully autonomous, with approximately 10 minutes of run time, and the ability to travel over 20 cm/s with DC motors and wheels. Communication to other TinyTeRP robots and stationary sensors is performed using a 2.4 GHz IEEE 802.15.4 radio. TinyTeRP has the ability to interface with additional sensors modules and locomotion actuators, including a wheeled locomotion and inertial measurement unit (IMU) module. An additional legged platform module that uses thermally actuated polymer legs with a silver composite acrylic is discussed. Finally, TinyTeRP demonstrates the use of two control algorithms to interact with a fixed beacon using received signal strength indicator (RSSI)
A Novel Lockable Spring-loaded Prismatic Spine to Support Agile Quadrupedal Locomotion
This paper introduces a way to systematically investigate the effect of
compliant prismatic spines in quadrupedal robot locomotion. We develop a novel
spring-loaded lockable spine module, together with a new Spinal
Compliance-Integrated Quadruped (SCIQ) platform for both empirical and
numerical research. Individual spine tests reveal beneficial spinal
characteristics like a degressive spring, and validate the efficacy of a
proposed compact locking/unlocking mechanism for the spine. Benchmark vertical
jumping and landing tests with our robot show comparable jumping performance
between the rigid and compliant spines. An observed advantage of the compliant
spine module is that it can alleviate more challenging landing conditions by
absorbing impact energy and dissipating the remainder via feet slipping through
much in cat-like stretching fashion.Comment: To appear in 2023 IEEE IRO
Martian Lava Tube Exploration Using Jumping Legged Robots: A Concept Study
In recent years, robotic exploration has become increasingly important in
planetary exploration. One area of particular interest for exploration is
Martian lava tubes, which have several distinct features of interest. First, it
is theorized that they contain more easily accessible resources such as water
ice, needed for in-situ utilization on Mars. Second, lava tubes of significant
size can provide radiation and impact shelter for possible future human
missions to Mars. Third, lava tubes may offer a protected and preserved view
into Mars' geological and possible biological past. However, exploration of
these lava tubes poses significant challenges due to their sheer size,
geometric complexity, uneven terrain, steep slopes, collapsed sections,
significant obstacles, and unstable surfaces. Such challenges may hinder
traditional wheeled rover exploration. To overcome these challenges, legged
robots and particularly jumping systems have been proposed as potential
solutions. Jumping legged robots utilize legs to both walk and jump. This
allows them to traverse uneven terrain and steep slopes more easily compared to
wheeled or tracked systems. In the context of Martian lava tube exploration,
jumping legged robots would be particularly useful due to their ability to jump
over big boulders, gaps, and obstacles, as well as to descend and climb steep
slopes. This would allow them to explore and map such caves, and possibly
collect samples from areas that may otherwise be inaccessible. This paper
presents the specifications, design, capabilities, and possible mission
profiles for state-of-the-art legged robots tailored to space exploration.
Additionally, it presents the design, capabilities, and possible mission
profiles of a new jumping legged robot for Martian lava tube exploration that
is being developed at the Norwegian University of Science and Technology.Comment: 74rd International Astronautical Congress (IAC
A Novel Bioinspired PVDF Micro/Nano Hair Receptor for a Robot Sensing System
This paper describes the concept and design of a novel artificial hair receptor for the sensing system of micro intelligent robots such as a cricket-like jumping mini robot. The concept is inspired from the natural hair receptor of animals, also called cilium or filiform hair by different research groups, which is usually used as a vibration receptor or a flow detector by insects, mammals and fishes. The suspended fiber model is firstly built and the influence of scaling down is analyzed theoretically. The design of this artificial hair receptor is based on aligned suspended PVDF (polyvinylidene fluoride) fibers, manufactures with a novel method called thermo-direct drawing technique, and aligned suspended submicron diameter fibers are thus successfully fabricated on a flexible Kapton. In the post process step, some key problems such as separated electrodes deposition along with the fiber drawing direction and poling of micro/nano fibers to impart them with good piezoeffective activity have been presented. The preliminary validation experiments show that the artificial hair receptor has a reliable response with good sensibility to external pressure variation and, medium flow as well as its prospects in the application on sensing system of mini/micro bio-robots
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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
A Unified Perspective on Multiple Shooting In Differential Dynamic Programming
Differential Dynamic Programming (DDP) is an efficient computational tool for
solving nonlinear optimal control problems. It was originally designed as a
single shooting method and thus is sensitive to the initial guess supplied.
This work considers the extension of DDP to multiple shooting (MS), improving
its robustness to initial guesses. A novel derivation is proposed that accounts
for the defect between shooting segments during the DDP backward pass, while
still maintaining quadratic convergence locally. The derivation enables
unifying multiple previous MS algorithms, and opens the door to many smaller
algorithmic improvements. A penalty method is introduced to strategically
control the step size, further improving the convergence performance. An
adaptive merit function and a more reliable acceptance condition are employed
for globalization. The effects of these improvements are benchmarked for
trajectory optimization with a quadrotor, an acrobot, and a manipulator. MS-DDP
is also demonstrated for use in Model Predictive Control (MPC) for dynamic
jumping with a quadruped robot, showing its benefits over a single shooting
approach
Contact-Implicit Trajectory Optimization using an Analytically Solvable Contact Model for Locomotion on Variable Ground
This paper presents a novel contact-implicit trajectory optimization method
using an analytically solvable contact model to enable planning of interactions
with hard, soft, and slippery environments. Specifically, we propose a novel
contact model that can be computed in closed-form, satisfies friction cone
constraints and can be embedded into direct trajectory optimization frameworks
without complementarity constraints. The closed-form solution decouples the
computation of the contact forces from other actuation forces and this property
is used to formulate a minimal direct optimization problem expressed with
configuration variables only. Our simulation study demonstrates the advantages
over the rigid contact model and a trajectory optimization approach based on
complementarity constraints. The proposed model enables physics-based
optimization for a wide range of interactions with hard, slippery, and soft
grounds in a unified manner expressed by two parameters only. By computing
trotting and jumping motions for a quadruped robot, the proposed optimization
demonstrates the versatility for multi-contact motion planning on surfaces with
different physical properties.Comment: in IEEE Robotics and Automation Letter
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