The aerodynamics and control of free flight manoeuvres in Drosophila
authors: Michael H. Dickinson, Florian T. Muijres
doi: 10.1098/rstb.2015.0388
CITATION
Dickinson, M. H., & Muijres, F. T. (2016). The aerodynamics and control of free flight manoeuvres in Drosophila. Philosophical Transactions of the Royal Society B: Biological Sciences, 371(1704), 20150388. https://doi.org/10.1098/rstb.2015.0388
ABSTRACT
A firm understanding of how fruit flies hover has emerged over the past two decades, and recent work has focused on the aerodynamic, biomechanical and neurobiological mechanisms that enable them to manoeuvre and resist perturbations. In this review, we describe how flies manipulate wing movement to control their body motion during active manoeuvres, and how these actions are regulated by sensory feedback. We also discuss how the application of control theory is providing new insight into the logic and structure of the circuitry that underlies flight stability. This article is part of the themed issue ‘Moving in a moving medium: new perspectives on flight’.
fleeting notes
a simple feedback controller for motor action called a proportional controller
- a sensor measures a state variable (like angular velocity)
- compared to a desired set point (like zero angular velocity) to create an error signal
- error signal is scaled linearly to generate a compensatory motor response
a PID controller
-
error signal is processed in 3 pathways
- one applies proportional gain to the error signal
- one continuously integrates it
- another differentiates it
-
pathways converge to create a composite signal for a compensatory motor command
highlights
“flies contain no active joints in their wings and the path of the wingtip can be traced on the surface of a sphere”Page 2
“wing kinematics are conveniently described using three Euler angles in a stroke plane reference frame (stroke position, deviation and wing rotation angle; figure 1a–c)”Page 2
“Quasi-steady aerodynamic models predict the time history of mid-stroke forces with remarkable accuracy [23] (figure 1d,e), a fact that is due to the peculiar stability of a flow structure known as the leading edge vortex (LEV)”Page 3
“Fruit flies and other small hovering animals flap their wings with relatively high rotational velocity compared with their translational velocity [21], thus ensuring a low Ro number and large Coriolis effects”Page 3
“flies pay a very dear price in drag for the lift they generate by way of the LEV”Page 3
“Why fruit flies do not flap their wings faster is not entirely clear, but it is likely that flapping frequency is limited by the physiology of their indirect flight muscles”Page 3
“In other words, flies can only flap their wings so fast, so they must do so at a high angle of attack to generate sufficient lift, thereby suffering the consequences of high drag”Page 3
“In experiments on tethered flies, Go ̈ tz & Wandel [46] directly demonstrated that the orientation of the mean flight force vector remains fixed relative to the stroke plane and body axis”Page 3
“Drosophila employ a flight pattern consisting of straight segments interspersed with rapid changes in heading termed body saccades”Page 3
“The turns consist of four overlapping actions: (i) a rapid bank that redirects the mean force vector in the intended direction of motion, (ii) a counter-bank that rotates the force vector back to a more vertical orientation, (iii) a slower yaw rotation that aligns the body axis with the new direction of motion, and (iv) an increase in the total aerodynamic force.”Page 3
“An analysis of flight trajectories within a wind tunnel found that body saccades account for 80% of all changes in heading”Page 4
“banked turns provide a much faster means of changing direction”Page 4
“banked turns involve rotation about three axes and require throttle control, they are more complicated than a pure yaw tur”Page 4
“This flexibility in the escape response demonstrates that flies quickly transform visual information into a motor code that generates the appropriate combination of pitch and roll torque.”Page 4
“Sensory signals experienced by an animal due to its own deliberate actions are known as ‘reafference’”Page 5
“The subset of campaniform sensilla that are best positioned to detect Coriolis forces as the haltere oscillates are also those that make direct electrotonic synapses with a steering motor neuron that has been implicated in fast alterations of wing kinematics”Page 5
“This difference suggests that the flies’ ability to turn is not impaired by reafferent feedback during the bank and counter-bank—perhaps because these actions are too fast to be inhibited by compensatory visual reflexes”Page 5
“lternatively, perhaps the head motor system can adequately stabilize gaze during the bank and counter-bank [87], whereas suppression of the HS cells is required to enable the yaw correction at the end of the saccade.”Page 5
“The requisite actions may be conveniently broken down into four control modes: throttle (i.e. changes in mean force) and torque production around the roll, pitch and yaw axes.”Page 5
“They accomplish this primarily by increasing the amplitude and frequency of the stroke, the combined effect of which is to raise the mean velocity of the wings (figure 3a).”Page 6
“By contrast, inner-loop reflexes are necessary for maintaining a stable pose and velocity in the face of external and internal perturbations”Page 7
“flies possess multiple inner-loop circuits, the dynamics of which are determined by the inertia and damping associated with each degree of freedom.”Page 7