Browsing by Subject "Rough terrain"

Now showing 1 - 3 of 3

Open Access
Design, manufacturing, and rough terrain analysis of a collision resilient foldable, adjustable wheeled miniature robot: FAWSCY
(2021-01) Demir, Didem Fatma
FAWSCY: Foldable Adjustable Wheeled Stringy Clumsy Robot is a foldable, collision resilient, adjustable wheeled robot which can run through diﬀerent ter-rains and inclined surfaces, to inspect areas which are unavailable to humans due to dimensional limitations or hazardousness level; to attend search and rescue missions to cover more area in a shorter duration and to be a part of somatic activities with elders and kids. Hence, it is desired to be non-harmful to itself and its environment in case of any collisions or falls, and persistent on its run under various conditions and terrains as any insect or lizard can. FAWSCY is an incremental work that till attaining its ﬁnal version, several legs and wheels; and electronic components and their combinations are investi-gated. First, c-legs are tested due to its advantages on rough terrains, yet they lack sensor implementation by its constant oscillatory movement. Then ninja stars are tested the robot yet they are so rigid that they sunder from the body in presence of a collision or undesired tracking. Afterwards, the bellow design is modiﬁed to be enforced as a wheel and it is the most promising wheel conﬁgu-ration since it can damp all longitudinal, lateral and vertical forces during the impact of a collision and fall. Also, it has appreciable rough terrain performance. However, as well as being soft it is also quite strong that it cannot be controlled for diﬀerent length conﬁgurations for a miniature untethered scale. Therefore, it is not applicable for FAWSCY. On its ﬁnal adjustable wheel, a novel wicker modular wheel design which exhibits similar behaviour with the bellow design, and its adjusting mechanism are proposed. On the other hand, Raspberry Pi is chosen to be the main processor, and by experiments and investigation through diﬀerent motors, sensors and control strategies, a two part single board design is ﬁnalized. The body of FAWSCY is also kirigami-inspired and formed by foldable sheets to cover and maintain integrity of its parts and components. After the design is completed, its performance and capabilities are assessed. First, its indoor run performance, wheel adjustment mechanism, collision resilient properties, obstacle scaling and response to inclination are investigated. The robot is assessed to be suitable for indoor environments, stairs and inclinations without getting disintegrated and harming other living subjects. Then, rough terrain experiments are conducted which resulted in success on grass, gravel and soil terrains with diverse wheel length conﬁgurations.
Open Access
Efficient bipedal locomotion on rough terrain via compliant ankle actuation with energy regulation
(Institute of Physics Publishing Ltd., 2021-08-12) Kerimoğlu, Deniz; Karkoub, M.; Uyanik, I.; Morgül, Ömer; Saranli, U.
Legged locomotion enables robotic platforms to traverse on rough terrain, which is quite challenging for other locomotion types, such as in wheeled and tracked systems. However, this benefit—moving robustly on rough terrain—comes with an inherent drawback due to the higher cost of transport in legged robots. The ultimate need for energy efficiency motivated the utilization of passive dynamics in legged locomotion. Nevertheless, a handicap in passive dynamic walking is the fragile basin of attraction that limits the locomotion capabilities of such systems. There have been various extensions to overcome such limitations by incorporating additional actuators and active control approaches at the expense of compromising the benefits of passivity. Here, we present a novel actuation and control framework, enabling efficient and sustained bipedal locomotion on significantly rough terrain. The proposed approach reinforces the passive dynamics by intermittent active feedback control within a bio-inspired compliant ankle actuation framework. Specifically, we use once-per-step energy regulation to adjust the spring precompression of the compliant ankle based on the liftoff instants—when the toe liftoffs from the ground—of the locomotion. Our results show that the proposed approach achieves highly efficient (with a cost of transport of 0.086) sustained locomotion on rough terrain, withstanding height variations up to 15% of the leg length. We provide theoretical and numerical analysis to demonstrate the performance of our approach, including systematic comparisons with the recent and state-of-the-art techniques in the literature.
Open Access
Stability and control of a compass gait model walking with series-elastic ankle actuation
(2017-11) Kerimoğlu, Deniz
Passive dynamic walking models are capable of capturing basic properties of walking behaviors and can generate stable human-like walking without any actuation on downhill surfaces. The passive compass gait model is among the simplest of such models, consisting of a planar point mass and two stick legs. A number of di erent actuation methods have been proposed both for this model and its more complex extensions to eliminate the need for a downhill sloped ground, balancing collision losses using gravitational potential energy. In this thesis, we introduce and investigate an extended compass gait model with series-elastic actuation at the ankle towards a similar goal, realizing stable walking on various terrains such as level ground, inclined surfaces and rough terrains. Our model seeks to capture the basic structure of how humans utilize toe push-o prior to leg lifto , and is intended to eventually be used for controlling the ankle joint in a lower-body robotic orthosis. We derive hybrid equations of motion for this model and obtain limit cycle walking on level and inclined grounds. We then numerically identify xed points of this system and and show numerically through Poincar e analysis that it can achieve asymptotically stable walking on level and inclined ground for certain choices of system parameters. The dependence of limit cycles and their stability on system parameters such as spring precompression and sti ness for level ground walking is identi ed by studying the bifurcation regimes of period doubling of this model, leading to chaotic walking patterns. We show that feedback control on the initial extension of the series ankle spring can be used to improve and extend system stability on level ground walking. Then, we investigate and identify the period doubling bifurcation regions of our model for spring precompression and ground slope parameter leading to various maps that we utilize for rough terrainwalking. Furthermore, we evaluate the performance of our model on rough terrains by applying ground slope feedback controllers on the spring precompression. Thereafter, we demonstrate that slope feedback along with stance leg apex velocity feedback control on the extension of the series ankle spring improves walking performance on rough terrains. The implementation of series elastic actuation on the ankle joint is realized with an experimental instantiations of active ankle foot orthosis system for the patients walking unnaturally and ine ciently with impaired ankles. Finally, we integrate the active ankle foot orthosis platform with an active knee orthosis platform where the experimentation results indicate that the integrated platform can generate e cient walking patterns.