Donal Holland

Computational models of neural control are a powerful tool for evaluating principles of motor control that cannot be tested directly in conventional experimental settings. Current gait controllers struggle with physiological grounding and can replicate a small set of discrete behaviours. Objective: here we propose a new neural controller, the Internal Model-based Modular Controller, that can transition between multiple lower-limb motor tasks within a single simulation. The architecture comprises a simplified model of the Mesencephalic Locomotor Region, which activates different internal models. These internal models organise functional muscle synergies into task-specific networks that generate coordinated activity across multiple muscles. Results: the controller performs Stand-To-Walk-To-Stand and Stand-To-Backward Walking-To-Stand transitions and modulates gait speed within a simulation by adjusting a few control signals. The observed simulated biomechanics and muscle activation patterns are generally consistent with experimental observations. Conclusions: Our results show that the proposed modular architecture represents a plausible mechanism for producing heterogeneous motor behaviours.

Motor adaptations are useful for studying the way in which the lower limbs are controlled by the brain. However, motor adaptation paradigms for the lower limbs are typically based on locomotion tasks, where the necessity of maintaining postural stability is the main driver of adaptation and could possibly mask other underlying processes. In this study we investigated whether small temporal or spatial asymmetries can trigger motor adaptations during stationary cycling, where stability is not directly compromised. Fourteen healthy individuals participated in two experiments: in one of the experiments, the angle between the crank arms of the pedals was altered by 10° to induce a temporal asymmetry; in the other experiment, the length of the right pedal was shortened by 2.4 cm to induce a spatial asymmetry. We recorded the acceleration of the crank arms and the electromographic signals of 16 muscles (8 per leg). The analysis of the accelerometer data was used to investigate the presence of motor adaptations. Muscle synergy analysis was performed on each side to quantify changes in neuromuscular control. We found that motor adaptations are present in response to temporal asymmetries and are obtained by progressively shifting the activation patterns of two synergies on the right leg. Spatial asymmetries, on the other hand, appear to trigger a feedback-driven response that does not present an aftereffect. This response is characterized by a steplike decrease in activity in the right gastrocnemius when the asymmetry is present and likely reflects the altered task demands. NEW & NOTEWORTHY The processes driving lower limb motor adaptations are not fully clear, and previous research appears to indicate that adaptations are mainly driven by stability. We show that lower limb adaptations can be obtained also in the absence of an explicit balance threat. We also show that adaptations are present when kinematic error cannot be compensated for, suggesting the presence of intrinsic error measures regulating the timing of activation of the two legs.

This article presents a direct additive manufacturing method for composite material soft pneumatic actuators that are capable of performing a range of programmable motions. Commonly, molding is the method used to manufacture soft fluidic actuators. This is material, labor, and time intensive and lacks the design freedom to produce custom actuators efficiently. This article proposes an alternative semiautomated method of designing and manufacturing composite soft actuators. An affordable, open-source, desktop three-dimensional (3D) printer was modified into a four-axis, combined, fused deposition modeling, and paste extrusion printer. A Grasshopper 3D algorithm was devised to implement custom actuator designs according to user inputs, resulting in a G-code print file. Bending, contracting, and twisting motion actuators were parametrically designed and subsequently additively manufactured from silicone and thermoplastic elastomer (TPE) materials. Experimental testing was completed on these actuators along with their constitutive materials. Finite element models were created to simulate the actuator's kinematic performance. Having a platform method to digitally configure and directly additively manufacture custom-motion, composite soft actuators has the potential to accelerate the development of more intricate designs and lead to potential impacts in a range of areas, including in-clinic personalization of soft assistive devices and patient-specific biomedical devices.

Hamstring injuries are common in field sport athletes. Eccentric strength training of the hamstring muscles is an integral component of rehabilitation programs. The Askling L‐Protocol comprises three exercises [extender; diver; glider] that load the hamstrings during eccentric activity. When compared to a conventional exercise‐based rehabilitation program, the Askling L‐Protocol has been shown to reduce the time to return to sport following hamstring injury and prevalence of injury recurrence. Nevertheless, the mechanisms behind its efficacy have yet to be studied. In this work, we conducted a kinematic and electromyographic analysis of the exercises of the Askling L‐Protocol. Eleven healthy individuals performed each of the exercises while electromyographic data from four muscles (including two hamstring muscles) were recorded. Hip and knee angular displacements and velocities were also synchronously recorded using a motion capture system. We found that the L‐Protocol elicits a maximal contraction (up to 60% of the MVC in the glider exercise) in the hamstring muscles at a work point similar to the swing phase of running (around 62 degrees hip flexion and 23 degrees knee flexion). No difference in the levels of activation of the hamstrings was observed between the diver and glider, regardless of the different functional role they had in the two exercises. During the extender, the hamstring muscles are stretched and minimally engaged. Finally, co‐activation analysis highlighted that through the combination of passive stretch and active eccentric contraction, the hamstrings are trained to co‐activate using similar structural modules employed differentially to drive the movement or stabilize it.

Soft actuators are ideal candidates for wearable biomedical devices, their inherent compliance, robustness, lightweight and the possibility to be washable take advantage over rigid actuators. Thus, a soft pneumatic fabric-polymer bending actuator as a base component for a robotic device for lymphedema treatment is reported in this work. The actuator is composed of two mechanical elements, one made of fabric and the other one made of a hyperelastic polymer which is stuck on the fabric element. The fabric element is designed and fabricated with a curved shape longer than the polymer element, that is a hyperelastic beam. To assemble both elements, the fabric element was folded before sticking in order to match the length of the polymer beam. Once the air is pumped into the fabric, it bends towards its original curved shape. Once the air is removed, the hyperelastic beam allows the actuator to recover its initial position. This actuator is capable of exerting compression and lateral force on a human arm mimicking manual lymphatic drainage. A mathematical model is presented which is in good agreement with the experimental data, it could serve to predict the actuator motion. An end-tip free bending displacement of about 2.2 cm and a bending force of about 0.35 N were achieved at 12.5 kPa. A proof-of-concept system for lymphedema treatment is presented as well.

The interpretation and reuse of previous design solutions, or precedents, is central to design. This paper describes qualitative research conducted over three years at two institutions, aimed at investigating the role of design knowledge re-use in project-based mechanical design courses. Research data were collected through participant observation, student interviews, anonymous questionnaires, and website analytics. The paper identifies challenges that must be addressed in order to support novice engineers in rehearsing the types of knowledge required to successfully reason about and engage with design precedents. Two categories of design precedents are identified: concept precedents and detail precedents. Providing students with access to the latter is identified as a particular challenge, as is providing students with access to engineering communities of practice. Approaches to addressing these challenges are discussed.

The Soft Robotics Toolkit (SRT) is an open-access website containing detailed information about the design, fabrication, and characterization of soft-robotic components and systems (Figure 1). Soft robotics is a growing field of research concerned with the development of electromechanical technology composed of compliant materials or structures. The SRT website hosts design files, multimedia fabrication instructions, and software tutorials submitted by an international community of soft-robotics researchers and designers. In this article, we describe the development of the SRT and some challenges in developing widely disseminated robotic-hardware resources. Our attempts to overcome these challenges in the development of the toolkit are discussed by focusing on strategies that have been used to engage participants ranging from K-12 grade students to robotics research groups. A series of design competitions encouraged people to use and contribute to the toolkit. New fabrication methods requiring only low-cost and accessible materials were developed to lower the entry barriers to soft robotics and instructional materials and outreach activities were used to engage new audiences. We hope that our experiences in developing and scaling the toolkit may serve as guidance for other open robotic-hardware projects.