LeggedWalking on Inclined Surfaces

The main contribution of this MS Thesis is centered around taking steps towards successful multi-modal demonstrations using Northeastern's legged-aerial robot, Husky Carbon. This work discusses the challenges involved in achieving multi-modal locomotion such as trotting-hovering and thruster-assisted incline walking and reports progress made towards overcoming these challenges. Animals like birds use a combination of legged and aerial mobility, as seen in Chukars' wing-assisted incline running (WAIR), to achieve multi-modal locomotion. Chukars use forces generated by their flapping wings to manipulate ground contact forces and traverse steep slopes and overhangs. Husky's design takes inspiration from birds such as Chukars. This MS thesis presentation outlines the mechanical and electrical details of Husky's legged and aerial units. The thesis presents simulated incline walking using a high-fidelity model of the Husky Carbon over steep slopes of up to 45 degrees.Comment: Masters thesi

Experimental tests on operation performance of a LARM leg mechanism with 3-DOF parallel architecture

Abstract. In this paper, a prototype of a LARM leg mechanism is proposed by using a tripod manipulator and its operation performance is investigated through lab experimental tests. In particular, an experimental layout is presented for investigating operational performance. A prescribed motion with an isosceles trapezoid trajectory is used for characterizing the system behavior. Experiment results are analyzed for the purpose of operation evaluation and architecture design characterization of the tripod manipulator and its proposed prototype

Design, control, and pilot study of a lightweight and modular robotic exoskeleton for walking assistance after spinal cord injury

Walking rehabilitation using exoskeletons is of high importance to maximize independence and improve the general well-being of spinal cord injured subjects. We present the design and control of a lightweight and modular robotic exoskeleton to assist walking in spinal cord injured subjects who can control hip flexion, but lack control of knee and ankle muscles. The developed prototype consists of two robotic orthoses, which are powered by a motor-harmonic drive actuation system that controls knee flexion–extension. This actuation module is assembled on standard passive orthoses. Regarding the control, the stance-to-swing transition is detected using two inertial measurement units mounted on the tibial supports, and then the corresponding motor performs a predefined flexion–extension cycle that is personalized to the specific patient’s motor function. The system is portable by means of a backpack that contains an embedded computer board, the motor drivers, and the battery. A preliminary biomechanical evaluation of the gait-assistive device used by a female patient with incomplete spinal cord injury at T11 is presented. Results show an increase of gait speed (+24.11%), stride length (+7.41%), and cadence (+15.56%) when wearing the robotic orthoses compared with the case with passive orthoses. Conversely, a decrease of lateral displacement of the center of mass (-19.31%) and step width (-13.37% right step, -8.81% left step) are also observed, indicating gain of balance. The biomechanical assessment also reports an overall increase of gait symmetry when wearing the developed assistive device.Peer ReviewedPostprint (published version

System Identification of Bipedal Locomotion in Robots and Humans

The ability to perform a healthy walking gait can be altered in numerous cases due to gait disorder related pathologies. The latter could lead to partial or complete mobility loss, which affects the patients’ quality of life. Wearable exoskeletons and active prosthetics have been considered as a key component to remedy this mobility loss. The control of such devices knows numerous challenges that are yet to be addressed. As opposed to fixed trajectories control, real-time adaptive reference generation control is likely to provide the wearer with more intent control over the powered device. We propose a novel gait pattern generator for the control of such devices, taking advantage of the inter-joint coordination in the human gait. Our proposed method puts the user in the control loop as it maps the motion of healthy limbs to that of the affected one. To design such control strategy, it is critical to understand the dynamics behind bipedal walking. We begin by studying the simple compass gait walker. We examine the well-known Virtual Constraints method of controlling bipedal robots in the image of the compass gait. In addition, we provide both the mechanical and control design of an affordable research platform for bipedal dynamic walking. We then extend the concept of virtual constraints to human locomotion, where we investigate the accuracy of predicting lower limb joints angular position and velocity from the motion of the other limbs. Data from nine healthy subjects performing specific locomotion tasks were collected and are made available online. A successful prediction of the hip, knee, and ankle joints was achieved in different scenarios. It was also found that the motion of the cane alone has sufficient information to help predict good trajectories for the lower limb in stairs ascent. Better estimates were obtained using additional information from arm joints. We also explored the prediction of knee and ankle trajectories from the motion of the hip joints

Overcoming barriers and increasing independence: service robots for elderly and disabled people

This paper discusses the potential for service robots to overcome barriers and increase independence of elderly and disabled people. It includes a brief overview of the existing uses of service robots by disabled and elderly people and advances in technology which will make new uses possible and provides suggestions for some of these new applications. The paper also considers the design and other conditions to be met for user acceptance. It also discusses the complementarity of assistive service robots and personal assistance and considers the types of applications and users for which service robots are and are not suitable

Design of Low-Cost Modular Bio-Inspired Electric–Pneumatic Actuator (EPA)-Driven Legged Robots

Exploring the fundamental mechanisms of locomotion extends beyond mere simulation and modeling. It necessitates the utilization of physical test benches to validate hypotheses regarding real-world applications of locomotion. This study introduces cost-effective modular robotic platforms designed specifically for investigating the intricacies of locomotion and control strategies. Expanding upon our prior research in electric–pneumatic actuation (EPA), we present the mechanical and electrical designs of the latest developments in the EPA robot series. These include EPA Jumper, a human-sized segmented monoped robot, and its extension EPA Walker, a human-sized bipedal robot. Both replicate the human weight and inertia distributions, featuring co-actuation through electrical motors and pneumatic artificial muscles. These low-cost modular platforms, with considerations for degrees of freedom and redundant actuation, (1) provide opportunities to study different locomotor subfunctions—stance, swing, and balance; (2) help investigate the role of actuation schemes in tasks such as hopping and walking; and (3) allow testing hypotheses regarding biological locomotors in real-world physical test benches

Partitioning the Mechanical Cost of Human Walking: Unveiling Cost Asymmetries for Bionic Technologies

Biomechanics studies over the past 150 years, suggest that animals, including humans, move at speeds that “optimize” their cost of transport. These optimizations can be metabolic, mechanical, or a mixture of the two; however, the consensus on the relationship between metabolic and mechanical cost has been muddied by our current conceptualizations of mechanical cost. Our prior considerations in assessing mechanical cost of transport for animal locomotion often rely upon the exchange of potential and kinetic energy for a rising and falling center of mass that is supported by rigid legs. As a result, our understanding of the mechanical costs associated with two-legged walking, especially the like that of humans, remains incomplete. Established approaches model only the mechanical cost of the step-to- step transitions, and often neglect or minimalize the cost dynamics that occur during steps. In an effort to rectify our current assumptions about mechanical cost, I examine the walking gaits of people through the lens of a quantitative approach that considers every instance of the walking stride as a whole. Direct measurement of ground reaction force and center of mass velocity vector geometries provides an opportunity to quantify the fundamental mechanical cost of transport dynamics that are inherent to human walking. The novel aspect of my approach allows for the partitioning of the human walking stride into steps (single support periods) and step-to-step transitions (double support periods). My approach allows us to better ascertain each support periods’ respective contributions to the overall mechanical work that is inherent to moving our body weight over a unit of distance in two steps – i.e. the mechanical cost of transport. My studies on human volunteers include experimental perturbations of walking speed and I also consider the effect of foot-ankle prosthetic devices on people with below-the-knee amputations. After establishing mechanical cost of transport dynamics on able-bodied volunteers walking at different speeds, I compare these results to the walking gaits of people using non-motorized, dynamic prosthetics and found that while mechanical costs of transport did not greatly differ between the two groups, the distribution of mechanical cost throughout the walking stride for prosthesis users was quite asymmetric. These cost asymmetries often resulted in “hot spots” of mechanical cost that have the potential to be rectified through mechanical intervention in the form of mechanical tuning or robotic prosthetic applications. I show this potential through the experimental examination of a prototype, powered prosthesis that was designed to emulate human ankle dynamics at different walking speeds. The results of the robotic intervention showed a 12%-17% decrease in overall mechanical cost of transport for prosthesis users versus their walking gait solutions on their traditional, non-motorized prosthesis. The results of this mechanical cost analysis along with stride partitioning to identify asymmetrical cost distribution is a key innovation for the analysis of human locomotion and has potential to bolster the foundation for future consideration of mechanical cost of transport dynamics in people using prosthetics, and in the development of robotic and movement assistance technologies

Octopus-inspired multi-arm robotic swimming

The outstanding locomotor and manipulation characteristics of the octopus have recently inspired the development, by our group, of multi-functional robotic swimmers, featuring both manipulation and locomotion capabilities, which could be of significant engineering interest in underwater applications. During its little-studied arm-swimming behavior, as opposed to the better known jetting via the siphon, the animal appears to generate considerable propulsive thrust and rapid acceleration, predominantly employing movements of its arms. In this work, we capture the fundamental characteristics of the corresponding complex pattern of arm motion by a sculling profile, involving a fast power stroke and a slow recovery stroke. We investigate the propulsive capabilities of a multi-arm robotic system under various swimming gaits, namely patterns of arm coordination, which achieve the generation of forward, as well as backward, propulsion and turning. A lumped-element model of the robotic swimmer, which considers arm compliance and the interaction with the aquatic environment, was used to study the characteristics of these gaits, the effect of various kinematic parameters on propulsion, and the generation of complex trajectories. This investigation focuses on relatively high-stiffness arms. Experiments employing a compliant-body robotic prototype swimmer with eight compliant arms, all made of polyurethane, inside a water tank, successfully demonstrated this novel mode of underwater propulsion. Speeds of up to 0.26 body lengths per second (approximately 100 mm s(-1)), and propulsive forces of up to 3.5 N were achieved, with a non-dimensional cost of transport of 1.42 with all eight arms and of 0.9 with only two active arms. The experiments confirmed the computational results and verified the multi-arm maneuverability and simultaneous object grasping capability of such systems