Design of compact switchable magnetic grippers for the HyReCRo structure-climbing robot

Planificación de trayectorias de un robot móvil modular con un único actuador

“…Según se observa, para valores pequeños de (es decir, usando unidades de adhesión que tardan poco en pegarse o despegarse), el tiempo mínimo se logra para valores de entre 50º y 150º, aproximadamente (para cada , el mínimo de se representa en la Figura 12b como un punto negro). Para valores suficientemente grandes de (para > 7 s aproximadamente), es decir, para unidades de adhesión que toman algo de tiempo para pegarse o despegarse (por ejemplo, como ocurre con los imanes permanentes conmutables mecánicamente [8]), el mínimo tiempo se logra siempre aplicando rotaciones de = 180º al robot. Cabe destacar en la Figura 12b que, incluso para valores pequeños de , el tiempo obtenido para = 180º es solo ligeramente superior al tiempo mínimo que se obtendría al tomar el ángulo óptimo para esos valores de .…”

Trajectory Analysis for the MASAR: A New Modular and Single-Actuator Robot

“…If the MASAR robot is used for exploring industrial infrastructures, made of ferromagnetic materials, then the best choice will be magnetic adhesion, preferably switchable permanent magnets [22]. As illustrated in Figure 3a, switchable magnets are made of cylindrical and diametrically magnetized permanent magnets embedded inside a ferromagnetic housing such that, by rotating by 180 • , one of the magnets with respect to the other using a micromotor, their magnetic poles remain parallel or anti-parallel, recirculating the magnetic flux either through the ferromagnetic medium (ON state: producing the adhesion to it) or internally through the housing (OFF state: canceling adhesion).…”

“…Switchable magnets have many advantages over classical electromagnets [23], such as lower energy consumption (power is only needed for switching the adhesion state, instead of continuously draining power to remain attached), higher adhesion forces per unit mass, and higher safety (in the event of power failure, permanent magnets will not detach). Examples of binary switchable magnets were developed in [22] for a climbing biped robot.…”

“…If the adhesion state of the pads of the robot changes simultaneously (or in the wrong order), the robot may temporarily lose control of its motion (and fall down, if it was climbing). In the case of adhesion devices that take some time to switch their adhesion states (such as switchable magnets [22]), in order to save time, it may be possible to partially overlap the attaching and detaching processes of both pivots without compromising the stability of the adhesion, instead of executing these processes sequentially. In any case, here we will not need to specify the precise sequence to switch the adhesion states of the pivots of the MASAR robot: it will suffice to model this process through the overall time T S necessary to complete it.…”

“…Returning to the graph of Figure 10a, this graph represents the minimum of τ for each time T S by a small black dot, which is attained for the optimal angle α * . According to this figure, for small switching times T S ≈ 0.1 s (i.e., for fast adhesion mechanisms that have small attachment/detachment times), the optimal angle α * is about 60 • , and this optimal angle quickly increases with T S until it stabilizes at α * = 131 • for sufficiently large values of T S (which would be the case of adhesion devices that take some time to switch between their adhesion states, such as switchable permanent magnets [22]).…”