Experiment-based kinematic validation of numeric modeling and simulated control of an untethered biomimetic microrobot in channel

Modeling and control of swimming untethered microrobots are important for future therapeutic medical applications. Bio-inspired propulsion methods emerge as realistic substitutes for hydrodynamic thrust generation in micro realm. Accurate modeling, power supply, and propulsion-means directly affect microrobot motility and maneuverability. In this work, motility of bacteria-like untethered helical microrobots in channels is modeled with the resistive force theory coupled with motor dynamics. Results are validated with private experiments conducted on cm-scale prototypes fully submerged in Si-oil filled glass channel. Li-Po battery is utilized as the onboard power supply. Helical tail rotation is triggered by an IR remote control. It is observed that time-averaged velocities calculated by the model agree well with experimental results. Finally, time-dependent performance of a hypothetical model-based position control scheme is simulated with upstream flow as disturbance

Concept, modeling and experimental characterization of the modulated friction inertial drive (MFID) locomotion principle:application to mobile microrobots

A mobile microrobot is defined as a robot with a size ranging from 1 in3 down to 100 µm3 and a motion range of at least several times the robot's length. Mobile microrobots have a great potential for a wide range of mid-term and long-term applications such as minimally invasive surgery, inspection, surveillance, monitoring and interaction with the microscale world. A systematic study of the state of the art of locomotion for mobile microrobots shows that there is a need for efficient locomotion solutions for mobile microrobots featuring several degrees of freedom (DOF). This thesis proposes and studies a new locomotion concept based on stepping motion considering a decoupling of the two essential functions of a locomotion principle: slip generation and slip variation. The proposed "Modulated Friction Inertial Drive" (MFID) principle is defined as a stepping locomotion principle in which slip is generated by the inertial effect of a symmetric, axial vibration, while the slip variation is obtained from an active modulation of the friction force. The decoupling of slip generation and slip variation also has lead to the introduction of the concept of a combination of on-board and off-board actuation. This concept allows for an optimal trade-off between robot simplicity and power consumption on the one hand and on-board motion control on the other hand. The stepping motion of a MFID actuator is studied in detail by means of simulation of a numeric model and experimental characterization of a linear MFID actuator. The experimental setup is driven by piezoelectric actuators that vibrate in axial direction in order to generate slip and in perpendicular direction in order to vary the contact force. After identification of the friction parameters a good match between simulation and experimental results is achieved. MFID motion velocity has shown to depend sinusoidally on the phase shift between axial and perpendicular vibration. Motion velocity also increases linearly with increasing vibration amplitudes and driving frequency. Two parameters characterizing the MFID stepping behavior have been introduced. The step efficiency ηstep expresses the efficiency with which the actuator is capable of transforming the axial vibration in net motion. The force ratio qF evaluates the ease with which slip is generated by comparing the maximum inertial force in axial direction to the minimum friction force. The suitability of the MFID principle for mobile microrobot locomotion has been demonstrated by the development and characterization of three locomotion modules with between 2 and 3 DOF. The microrobot prototypes are driven by piezoelectric and electrostatic comb drive actuators and feature a characteristic body length between 20 mm and 10 mm. Characterization results include fast locomotion velocities up to 3 mm/s for typical driving voltages of some tens of volts and driving frequencies ranging from some tens of Hz up to some kHz. Moreover, motion resolutions in the nanometer range and very low power consumption of some tens of µW have been demonstrated. The advantage of the concept of a combination of on-board and off-board actuation has been demonstrated by the on-board simplicity of two of the three prototypes. The prototypes have also demonstrated the major advantage of the MFID principle: resonance operation has shown to reduce the power consumption, reduce the driving voltage and allow for simple driving electronics. Finally, with the fabrication of 2 × 2 mm2 locomotion modules with 2 DOF, a first step towards the development of mm-sized mobile microrobots with on-board motion control is made

Computational and microhydrodynamic modeling and experiments with bio-inspired swimming robots in cylindrical channels

Modeling and control of swimming untethered micro robots are important for future therapeutic medical applications. Bio-inspired propulsion methods emerge as realistic substitutes for hydrodynamic thrust generation in micro realm. Accurate modeling, power supply, and propulsion-means directly affect the mobility and maneuverability of swimming micro robots with helical or planar wave propagation. Flow field around a bio-inspired micro swimmer comprised of a spherical body and a rotating helical tail is studied with time-dependent three-dimensional computational fluid dynamics (CFD) model. Analytical hydrodynamic studies on the bodies of well known geometries submerged in viscous flows reported in literature do not address the effect of hydrodynamic interactions between the body and the tail of the robot in unbounded viscous fluids. Hydrodynamic interactions are explained qualitatively and quantitatively with the help of CFD-model. A cm-scale powered bio-inspired swimmer robot with helical tails is manufactured including a payload and a replaceable rigid helical tail. The payload includes on-board power supply and remote-control circuitry. A number of helical tails with parameterized wave geometry are used. Swimmer performed in cylindrical channels of different diameters while fully submerged in an oil-bath of high viscosity. A real-time six degrees-of-freedom microhydrodynamic model is developed and implemented to predict the rigid-body motion of the swimming robots with helical and traveling-plane-wave tails. Results of microhydrodynamic models with alternative resistance coefficients are compared against CFD simulations and in-channel swimming experiments with different tails. Validated microhydrodynamic model is further employed to study efficient geometric designs with different wave propagation methods within a predefined design space

Using MapReduce Streaming for Distributed Life Simulation on the Cloud

Distributed software simulations are indispensable in the study of large-scale life models but often require the use of technically complex lower-level distributed computing frameworks, such as MPI. We propose to overcome the complexity challenge by applying the emerging MapReduce (MR) model to distributed life simulations and by running such simulations on the cloud. Technically, we design optimized MR streaming algorithms for discrete and continuous versions of Conway’s life according to a general MR streaming pattern. We chose life because it is simple enough as a testbed for MR’s applicability to a-life simulations and general enough to make our results applicable to various lattice-based a-life models. We implement and empirically evaluate our algorithms’ performance on Amazon’s Elastic MR cloud. Our experiments demonstrate that a single MR optimization technique called strip partitioning can reduce the execution time of continuous life simulations by 64%. To the best of our knowledge, we are the first to propose and evaluate MR streaming algorithms for lattice-based simulations. Our algorithms can serve as prototypes in the development of novel MR simulation algorithms for large-scale lattice-based a-life models.https://digitalcommons.chapman.edu/scs_books/1014/thumbnail.jp