Valter Böhm

Modelling of locomotion systems using deformable magnetizable media

This paper deals with the modelling and the realization of active and passive locomotion systems using the effects of the deformation of a magnetizable elastic material and the deformation of the surface of a membrane filled with a ferrofluid under the influence of a magnetic field. Prototypes implementing these principles have been constructed and proved positive. Theoretically (analytically and numerically) calculated results of the velocity of the mobile system are compared with the experimental data. Artificial worms based on these principles could be autonomous systems, and could be useful in medicine and in inspection technology.

Vibration-driven mobile robots based on single actuated tensegrity structures

This paper describes a new concept for locomotion of mobile robots based on single actuated tensegrity structures. To discuss the working principle, two vibration-driven locomotion systems are considered. Due to the complex dynamics of the applied tensegrity structures with pronounced mechanical compliance, the movement performance of both systems is highly dependent on the driving frequency. By using single-actuation, the system design and also their control can be kept simple. The movement of the robots is depending on their configuration uniaxial bidirectional or planar. The working principle of both systems is discussed with the help of transient dynamic analyses and verified with experimental tests for a selected prototype.

Compliant Multistable Tensegrity Structures with Simple Topologies

This paper describes a method to identify compliant tensegrity structures with multiple states of self-equilibrium. The considered algorithm is based on the repeated use of a form-finding procedure, using the static Finite-Element-Method. The algorithm can be used to develop compliant multistable tensegrity mechanisms with simple topologies. Therefore three planar tensegrity mechanisms with two or three stable equilibrium configurations are exemplary considered and verified experimentally.

Worm-like Locomotion Systems (WLLS) - Theory, Control and Prototypes

Most of biologically inspired locomotion systems are dominated by walking machines pedal locomotion. A lot of biological models (bipedal up to octopedal) are studied in the literature and their constructions were transferred by engineers in different forms of realization. Non-pedal forms of locomotion show their advantages in inspection techniques or in applications to medical technology for diagnostic systems and minimally invasive surgery (endoscopy). These areas of application were considered by (Choi et al., 2002), (Mangan et al., 2002), (Menciassi & Dario, 2003). Hence, this type of locomotion and its drive mechanisms are current topics of main focus. In this chapter we discuss the problem of developing worm-like locomotion systems, which have the earthworm as a living prototype, from two points of view: • modelling and controlling in various levels of abstraction, • designing of prototypes with classical and non-classical forms of drive.

Ferrofluid-based Flow Manipulation and Locomotion Systems

The article demonstrates some examples of locomotion systems with bifluidic flow control using ferrofluid. By controlling the change of shape, position, and pressure of the ferrofluid in a secondary low viscous fluid by magnetic fields locomotion of objects or the ferrofluid itself can be realized. The locomotion of an object is caused, in the first example, by a ferrofluid generated flow of the secondary fluid and in the second and third case by the direct alteration of the ferrofluid position.

On the Classification of Compliant Mechanisms

An intrinsic compliance of technical systems is often required in a lot of applications i.e. medical technology and man-machine interaction. This requirement can be realised constructively by utilisation of compliant mechanisms. This paper presents a classification of the deformation behaviour of compliant mechanisms to simplify their systematic construction. Especially focused on their enlarged functional properties, one objective is to minimize or replace the sensory effort by using “intelligent” mechanics, another one is to show future-oriented possibilities for their development.

Sensor placement with a telescoping compliant mechanism

The aim of this work is to develop a new compliant mechanism [1–3]. The observation of the snail (helix pomatia L.) provides the biological inspiration of a compliant mechanism consisting of silicone. For this an analytic model was generated. With the finite element method (FEM) the influence of design parameter variation and the variation of the used compliant material on motion behavior of the structure center under increasing internal pressure load was investigated. The motion behavior of the first prototype showed an acceptable quantitative and qualitative correlation with the simulation results.

Indoor locomotion experiments of a spherical mobile robot based on a tensegrity structure with curved compressed members

This work presents theoretical and experimental investigations on an untethered rolling tensegrity robot. Previous research has shown, that rolling locomotion of compliant tensegrity robots can be realized without change of their shape, by using only internal mass shifting. The use of simple tensegrity structures, based on curved compressed members enables pure rolling locomotion in contrast to the most known prototypes of this kind. Therefore, theoretical and experimental investigations of an untethered locomotion system based on a simple tensegrity structure, consisting of two disconnected compressed curved members connected to a continuous net of twelve prestressed tensioned members with pronounced elasticity, are considered. Planar locomotion is induced by the movement of only two drive units as internal masses along the curved compressed members. Theoretical considerations show the influence of the geometrical system parameters on the movement behavior of the system. With the help of experimental investigations, by using motion-capturing technique, main properties of the locomotion performance of a prototype are discussed.

Spherical mobile robot based on a tensegrity structure with curved compressed members

The use of mechanically compliant tensegrity structures in mobile robots is an attractive research topic. This paper describes a new concept for rolling locomotion of mobile robots based on tensegrity structures. In particular, an untethered locomotion system based on a simple tensegrity structure, consisting of two rigid disconnected compressed curved members connected to a continuous net of twelve prestressed tensioned members with pronounced elasticity, is considered. The locomotion is induced by the movement of two internal masses. The working principle of the system is discussed with the help of kinematic considerations and verified with experimental tests.

Theoretical and Experimental Investigations of Amoeboid Movement and First Steps of Technical Realisation

We report about the investigation of the amoeboid locomotion at Amoeba proteus. Based on the detailed experimental study of the internal cytoplasm flow and the variation of the contour of the amoeba with optical flow measurement techniques like particle image velocimetry (PIV) we found characteristic velocity fields and motions of the center of mass. Furthermore a peripheral cell model is developed, in which a contractile backward flow of actin-myosin in the cortex stabilizes cell polarity and locomotion by inducing more protrusions in the front and stronger retraction in the rear. The results from the experimental and theoretical study were used to realise prototypes of locomotion systems, composed of silicon elastomer body with controlled elasticity and driven by a magnetic system, based on amoeboid motion principles.