Performance and stability of fly-inspired, saccade-based hybrid control

In a way analogous to human vision, the fruit fly Drosophila melanogaster and many other flying insects generate smooth and saccadic movements to stabilize and shift their gaze in flight, respectively. It has been hypothesized that this combination of continuous and discrete movements benefits both flight stability and performance, particularly at high frequencies or speeds. Here we develop a hybrid control system model to explore the effects of saccades on the yaw stabilization reflex of D. melanogaster. Inspired from experimental data, the model includes a first order plant, a Proportional-Integral (PI) continuous controller, and a saccadic reset system that fires based on the integrated error of the continuous controller. We explore the gain, delay and switching threshold parameter space to quantify the optimum regions for stability and performance. We show that the addition of saccades to a continuous controller provides benefits to both stability and performance across a range of frequencies. Our model suggests that Drosophila operate near its optimal switching threshold for its experimental gain set. We also show that based on experimental data, D. melanogaster operates in a region that trades off performance and stability. This trade-off increases flight robustness to compensate for environmental uncertainties such as wing damage.

Developmental onset of a cerebellar-dependent forward model of movement in motor thalamus

To execute complex behavior with temporal precision, adult animals use internal models to predict the sensory consequences of self-generated movement. Here, taking advantage of the unique kinematic features of twitches-the brief, discrete movements of active sleep-we captured the developmental onset of a cerebellar-dependent internal model. Using rats at postnatal days (P) 12, P16, and P20, we compared neural activity in two thalamic structures: the ventral posterior (VP) and ventral lateral (VL) nuclei, both of which receive somatosensory input but only the latter of which receives cerebellar input. At all ages, twitch-related activity in VP lagged behind movement, consistent with sensory processing; similar activity was observed in VL through P16. At P20, however, VL activity precisely mimicked the twitch itself, a pattern of activity that depended on cerebellar input. Altogether, these findings implicate twitches in the development and refinement of internal models of movement.

Use of IMU in Differential Analysis of the Reverse Punch Temporal Structure in Relation to the Achieved Maximal Hand Velocity

To achieve good performance, athletes need to synchronize a series of movements in an optimal manner. One of the indicators used to monitor this is the order of occurrence of relevant events in the movement timeline. However, monitoring of this characteristic of rapid movement is practically limited to the laboratory settings, in which motion tracking systems can be used to acquire relevant data. Our motivation is to implement a simple-to-use and robust IMU-based solution suitable for everyday praxis. In this way, repetitive execution of technique can be constantly monitored. This provides augmented feedback to coaches and athletes and is relevant in the context of prevention of stabilization of errors, as well as monitoring for the effects of fatigue. In this research, acceleration and rotational speed signal acquired from a pair of IMUs (Inertial Measurement Unit) is used for detection of the time of occurrence of events. The research included 165 individual strikes performed by 14 elite and national-level karate competitors. All strikes were classified as slow, average, or fast based on the achieved maximal velocity of the hand. A Kruskal–Wallis test revealed significant general differences in the order of occurrence of hand acceleration start, maximal hand velocity, maximal body velocity, maximal hand acceleration, maximal body acceleration, and vertical movement onset between the groups. Partial differences were determined using a Mann–Whitney test. This paper determines the differences in the temporal structure of the reverse punch in relation to the achieved maximal velocity of the hand as a performance indicator. Detecting the time of occurrence of events using IMUs is a new method for measuring motion synchronization that provides a new insight into the coordination of articulated human movements. Such application of IMU can provide additional information about the studied structure of rapid discrete movements in various sporting activities that are otherwise imperceptible to human senses.

Effect of Geometrical Parameter Cutting Edge on the Toroidal Forming Surface of a Solid End Mill

Solid end mill with a toroidal forming section are the most productive solutions in the field of processing difficult-to-process materials. The process of forming the cutting geometry of such cutters is performed on grinding machines with CNC with the use of abrasive grinding wheels. The formation of the cutting edge on the toroidal section is carried out by discrete movements of the working bodies of the machine in accordance with the control program. The disadvantage of the stepper drive used in CNC machines is the limited discreteness of the described trajectory resulted in the loss of accuracy when forming radius, arc, spherical and toroidal sections. Loss of accuracy in the formation of elements of the working geometry of a solid end mill can negatively affect the tool life, and the structural strength of the joints of the transition of working surfaces. The study is aimed at identifying the necessary and sufficient number of points that describe the spatial shape of the cutting edge with acceptable loss of accuracy.

Basal Ganglia Circuits for Action Specification

Behavior is readily classified into patterns of movements with inferred common goals—actions. Goals may be discrete; movements are continuous. Through the careful study of isolated movements in laboratory settings, or via introspection, it has become clear that animals can exhibit exquisite graded specification to their movements. Moreover, graded control can be as fundamental to success as the selection of which action to perform under many naturalistic scenarios: a predator adjusting its speed to intercept moving prey, or a tool-user exerting the perfect amount of force to complete a delicate task. The basal ganglia are a collection of nuclei in vertebrates that extend from the forebrain (telencephalon) to the midbrain (mesencephalon), constituting a major descending extrapyramidal pathway for control over midbrain and brainstem premotor structures. Here we discuss how this pathway contributes to the continuous specification of movements that endows our voluntary actions with vigor and grace.

Metadata, Jailbreaking, and the Cybernetic Governmentality of iOS: Or, the Need to Distinguish Digital Privacy from digital privacy

Digital privacy tends to be understood as the “top-down” regulation and control of personal information on the behalf of corporate and governmental institutions, realized through various policies and practices. While smartphone manufacturers increasingly innovate and alter their policies and practices to reflect new and ongoing cyber challenges, they tend to emphasize the protection of personal information in the form of content data. On the other hand, there is metadata: the measurements and math of content data. Abundant and ubiquitous in their discrete movements, they are the most precious commodity in the world of big data mobile analytics. Smartphone metadata are also one of the most pressing privacy concerns precisely because it is exceedingly difficult to see, study, and analyze. However, there is another realm through which digital privacy exists: a realm where the inability to see and study metadata is unacceptable. This entirely differently realm is comprised of jailbreakers—a network of hacktivist programmers injecting software-based “tweaks” into Apple mobile devices in ways that reveal metadata to users and allow users to control them. By doing so, jailbreakers allow users to build previously unrealized relationships with metadata and thereby radically distinguishing “top-down” Digital Privacy from “bottom-up” digital privacy. Although Apple has routinely resisted jailbreaking citing fears over device instability, user security vulnerability, and Terms of Use violations, this article reveals that many key privacy-first jailbreaking tweaks undermine Apple’s ability to monopolize metadata flows. Theorised through a cybernetic governmentality, this intervention demonstrates the extents to which Apple goes to reify its profit-first vision of information protection, one which insulates many metadata flows from its users. Through this theoretical approach, we as analysts can critically glean awareness of the politics of the (in)visibility and (il)legibility of metadata and the role they play in the discourse on digital, mobile data protection.

COMPUTER TECHNOLOGY OF SYNTHESIS OPTIMAL LINEAR SWITCHED SYSTEMS

The linear-quadratic problem of synthesis optimal control of switched systems is considered. Continuous change of state of the system is described by linear differential equations, and instantaneous discrete changes of state (switching) – linear recurrent equations. The moments of switching, and their number is not prespecified. The quality of control is characterized by a quadratic functional, which takes into account the cost of each switch. The considered problem generalizes the classical linear-quadratic problems of optimal control of continuous, discrete and continuous-discrete systems, transferring them to a new class of dynamic systems – switchable (hybrid) control systems. Together with the problem of optimal control synthesis, the problem of minimizing the number of switchings, characteristic of hybrid systems, is relevant. The peculiarity of the synthesis of optimal switchable systems is that the price function in the considered problem is not quadratic. Therefore, it is proposed to build a price function from auxiliary, so-called price moment functions, each of which is defined as the minimum value of the quality functional at fixed switching moments and is quadratic. At the same time, the optimal positional control, linear in state, depends nonlinearly on switching moments. Optimization of these moments becomes the last stage of the synthesis. The proposed computer-aided synthesis technology makes it possible to find the optimal “controlling complex”, including the number of switches, the switching moments, as well as the control of continuous and discrete movements of the system. The application of the developed technology is demonstrated on an academic example of synthesis.

Effectiveness of the addition of rhythmic or discrete aiming movements training of the upper limbs on motor function and participation after stroke: protocol of a randomized controlled trial

Background Upper limb disabilities after a stroke compromise the activities of daily living. Several approaches to improve motor control and reduce disability are proposed, including specific unilateral training of the contralesional limb or bilateral training with appropriate equipment and/or robotic assistance. These approaches can be used with rhythmic or discrete movements along with usual therapy, but the most effective approach has never been determined. The objective of this study will be to verify the effect of training with rhythmic or discrete movements in conjunction with the usual therapy on motor function and participation regarding the patients’ upper limbs after chronic stroke. Methods/Design This is a 3-arm, assessor-blinded, randomized controlled trial. Seventy-five patients with chronic stroke (> 6 months) and upper limb paresis will be included. Participants will be randomly allocated into 3 groups: 1) discrete movement training and usual therapy (n = 25), 2) rhythmic movement training and usual therapy (n = 25) and 3) a control group, (n = 25) which will only receive the usual therapy. A five-week intervention period (10 sessions) with two sessions per week will be carried out. Outcome measures include participation, activity and motor function measured by the Stroke Impact Scale (SIS), Motor Activity Log (MAL) and Fugl-Meyer Scale, respectively; other measures are aiming movement performance, grip strength and spasticity, which will be obtained at follow-up assessments 5 weeks and 3 months after randomization. Discussion The results of this trial can support allied health professionals’ decision-making processes in the treatment of motor impairment and disability after chronic stroke and reduce this condition’s health-related costs.