Existing devices to assist upper extremity (UE) movement in infants with or at risk for motor impairments remain limited and are mainly passive devices. The aim of this project was to develop and assess the validity and reliability of the first-actuated wearable device for this population. A wearable device consisting of four pneumatic actuators (two per arm) was developed and tested on a custom-built physical model with articulated joints (four degrees-of-freedom (DOFs) per arm) based on an average 12-month-old infant's upper body. The device actively controls 2DOFs per arm (one at the elbow and one at the shoulder) and does not prohibit motion about the remaining non-actuated DOFs. Three distinct device actuator synergies, that resemble muscle recruitment strategies, were evaluated in a vertical reaching task using one arm and both arms. The device was assessed for its performance, wearability, and safety. Performance was assessed via the average duration, smoothness, and repeatability of reaching movements, and maximum range of motion per actuated joint. Wearability was assessed via kinematic compatibility to infant reaching trajectories. Safety was assessed via actuator durability. Results demonstrate the efficacy of the device and reveal key insights for further improvements.

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Micro Aerial Vehicles (MAVs) often face a high risk of collision during autonomous flight, particularly in cluttered and unstructured environments. To mitigate the collision impact on sensitive onboard devices, resilient MAVs with mechanical protective cages and reinforced frames are commonly used. However, compliant and impact-resilient MAVs offer a promising alternative by reducing the potential damage caused by impacts. In this study, we present novel findings on the impact-resilient capabilities of MAVs equipped with passive springs in their compliant arms. We analyze the effect of compliance through dynamic modeling and demonstrate that the inclusion of passive springs enhances impact resilience. The impact resilience is extensively tested to stabilize the MAV following wall collisions under high-speed and large-angle conditions. Additionally, we provide comprehensive comparisons with rigid MAVs to better determine the tradeoffs in flight by embedding compliance onto the robot's frame.

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Abstract-Repetitive control (RC) with linear phase lead compensation provides a simple but very effective control solution for any periodic signal with a known period. Multirate repetitive control (MRC) with a downsampling rate can reduce the need of memory size and computational cost, and then leads to a more feasible design of the plug-in repetitive control systems in practical applications. However, with fixed sampling rate, both MRC and its linear phase lead compensator are sensitive to the ratio of the sampling frequency to the frequency of interested periodic signals: (1) MRC might fails to exactly compensate the periodic signal in the case of a fractional ratio; (2) linear phase lead compensation might fail to enable MRC to achieve satisfactory performance in the case of a low ratio. In this paper, a universal fractional-order design of linear phase lead compensation MRC is proposed to tackle periodic signals with high accuracy, fast dynamic response, good robustness, and cost-effective implementation regardless of the frequency ratio, which offers a unified framework for housing various RC schemes in extensive engineering application. An application example of programmable AC power supply is explored to comprehensively testify the effectiveness of the proposed control scheme.Index Terms-repetitive control, DC/AC inverter, multirate repetitive control, phase lead compensation, Lagrange interpolation polynomial, programmable AC power supply

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Abstract-Repetitive control (RC) presents an attractive solution to achieve low steady-state tracking error and total harmonic distortion (THD) for periodic signals. For conventional RC (CRC), it requires that the ratio of reference signal period to the fixed sampling period to be an integer. Therefore, the reference signal with variable frequency or a fractional period ratio will lead to severe performance degradation. Although existing hardware variable sampling rate methods enable CRC to be frequency adaptive, the variable sampling frequency will also influence the overall system stability, and they need that the CPU has variable sampling frequency ability. In this paper, a flexible and easy-to-implement method, virtual variable sampling (VVS), is proposed to enable RC to be frequency adaptive. The proposed VVS method, which creates a virtual delay unit to approximate each variable sampling delay, achieves a flexible variable sampling as similar as hardware-based variable sampling, but it does not influence overall system sampling frequency and stability. Experimental results of a single phase DC/AC converter system are presented to show the effectiveness of the proposed VVS-RC.

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