Active Heading Control Platform for Instruments Flown on High Altitude Balloons

Experiments flown on high-altitude balloons are typically free to spin without any control or information collected on the payload orientation during flight, limiting the scope of experiments that can be performed. Projects that include targeting (i.e. imaging the 2017 solar eclipse) have at best a random chance of succeeding, while video footage is often hard to watch due to high payload rotation rates. While passive stabilization reduces the rotation rate, active pointing control is necessary for continuous target acquisition. Here we discuss a project built by students at Wright College called the Controlled Heading Automation Device (CHAD) that actively controls the heading of other instruments (i.e. cameras) and has been proven to work in flight. This project is open-source, 3D printable, made from cheap DIY electronics, and has been made available online (http://physi.cz/chad) so the high-altitude ballooning community can create, use, and adapt it to their own projects. We show how to create an attitude and heading reference system (AHRS) that can be used to continuously record payload orientation, which can supplement experiments where pointing information is needed. We then show how to have CHAD use the AHRS to automatically control the heading of other instruments in real-time without any other inputs.

Influence of the Passive Stabilization of the Trunk and Upper Limb on Selected Parameters of the Hand Motor Coordination, Grip Strength and Muscle Tension, in Post-Stroke Patients

Objective: Assessment of the influence of a stable trunk and the affected upper limb (dominant or non-dominant) on the parameters of the wrist and hand motor coordination, grip strength and muscle tension in patients in the subacute post-stroke stage compared to healthy subjects. Design: An observational study. Setting: Stroke Rehabilitation Department. Subjects: Thirty-four subjects after ischemic cerebral stroke and control group-32 subjects without neurological deficits, age and body mass/ height matched were included. Main measures: The tone of the multifidus, transverse abdominal and supraspinatus muscles were assessed by Luna EMG device. A HandTutor device were used to measure motor coordination parameters (e.g., range of movement, frequency of movement), and a manual dynamometer for measuring the strength of a hand grip. Subjects were examined in two positions: sitting without back support (non-stabilized) and lying with stabilization of the trunk and the upper limb. Results: Passive stabilization of the trunk and the upper extremity caused a significant improvement in motor coordination of the fingers (p ˂ 0.001) and the wrist (p < 0.001) in patients after stroke. Improved motor coordination of the upper extremity was associated with an increased tone of the supraspinatus muscle. Conclusions: Passive stabilization of the trunk and the upper limb improved the hand and wrist coordination in patients following a stroke. Placing patients in a supine position with the stability of the affected upper limb during rehabilitation exercises may help them to access latent movement patterns lost due to neurological impairment after a stroke.

Vibrational control: A hidden stabilization mechanism in insect flight

It is generally accepted among biology and engineering communities that insects are unstable at hover. However, existing approaches that rely on direct averaging do not fully capture the dynamical features and stability characteristics of insect flight. Here, we reveal a passive stabilization mechanism that insects exploit through their natural wing oscillations: vibrational stabilization. This stabilization technique cannot be captured using the averaging approach commonly used in literature. In contrast, it is elucidated using a special type of calculus: the chronological calculus. Our result is supported through experiments on a real hawkmoth subjected to pitch disturbance from hovering. This finding could be particularly useful to biologists because the vibrational stabilization mechanism may also be exploited by many other creatures. Moreover, our results may inspire more optimal designs for bioinspired flying robots by relaxing the feedback control requirements of flight.