Kick Control: Using the Attracting States Arising Within the Sensorimotor Loop of Self-Organized Robots as Motor Primitives

Abstract

Self-organized robots may develop attracting states within the sensorimotor loop, that is within the phase space of neural activity, body and environmental variables. Fixpoints, limit cycles and chaotic attractors correspond in this setting to a non-moving robot, to directed, and to irregular locomotion respectively. Short higher-order control commands may hence be used to kick the system from one self-organized attractor robustly into the basin of attraction of a different attractor, a concept termed here as kick control. The individual sensorimotor states serve in this context as highly compliant motor primitives. We study different implementations of kick control for the case of simulated and real-world wheeled robots, for which the dynamics of the distinct wheels is generated independently by local feedback loops. The feedback loops are mediated by rate-encoding neurons disposing exclusively of propriosensoric inputs in terms of projections of the actual rotational angle of the wheel. The changes of the neural activity are then transmitted into a rotational motion by a simulated transmission rod akin to the transmission rods used for steam locomotives. We find that the self-organized attractor landscape may be morphed both by higher-level control signals, in the spirit of kick control, and by interacting with the environment. Bumping against a wall destroys the limit cycle corresponding to forward motion, with the consequence that the dynamical variables are then attracted in phase space by the limit cycle corresponding to backward moving. The robot, which does not dispose of any distance or contact sensors, hence reverses direction autonomously.

Editorial: The roles of self-organization and sensory adaptation for locomotion in animals and robots

“…Valencia Urbina et al investigated the behavior of two-wheeled robots in a Braitenberg-style obstacle avoidance setup, but with a controller based on the connectome of C. elegans . In a general context, two-wheeled robots have been used for a wide range of purposes, such as the emergence of kick control (Sándor et al, 2018 ). Here, Valencia Urbina et al showed, that it is possible to transfer a biological network of neurons to a functioning robotic application.…”

Embodied robots driven by self-organized environmental feedback

“…where k is a spring constant and x ( a ) and x ( t ) , respectively, are the actual and the target positions of the wheel in terms of a projection to the ground (Sándor, Nowak, Koglin, Martin, & Gros, 2018). Note that the angle φ , which enters the right-hand side of equations (1) and (2) as cos ( φ ) , is the measured, actual angle of the wheel.…”

“…This is not a problem for simulated robots, for which ω is a directly accessible variable. To obtain a reliable estimate of the instantaneous angular velocity for real-world robots working with duty cycles of the order of 20 Hz would, however, be a challenge (Sándor, Nowak, Koglin, Martin, & Gros, 2018).…”

“…where k is a spring constant and x (a) and x (t) respectively the actual and the target position of the wheel in terms of a projection to the ground [29]. Note that the angle ϕ, which enters the right-hand side of Eqs.…”

When the goal is to generate a series of activities: A self-organized simulated robot arm

“…Self-organizing principles may be implemented within the sensorimotor loop [10], which is comprised of environment, body, actuator and sensory readings, with the latter being restricted in the pure case to propiosensation, viz to the internal state of the robot. The attractors self-stabilizing in the sensorimotor loop may then give rise to complex patterns of regular and of chaotic motion primitives [15], which can be selected in a second step using 'kick control' [16]. From a general perspective, kick control is an instance of a higher-level control mechanism exploiting the reduction in control complexity provided by morphologically computing robots [17,18].…”