Joachim Steigenberger

Gait generation considering dynamics for artificial segmented worms

This paper deals with terrestrial worm-like locomotion systems living in a straight line. They are modeled as chains of mass points having ground interaction via spikes which make the velocities unidirectional. A method is presented to construct gaits with any desired time pattern of resting mass points (which are acted on by the propulsive forces). Taking the dynamics into consideration, conclusions about the choice and shift of gaits in connection with actuator data are given.

Mathematical Model of Worm-like Motion Systems with Finite and Infinite Degree of Freedom

This paper presents some theoretical and practical investigations of worm-like motion systems that have the earthworm as live prototype. In the first part of the paper these systems are modeled in form of straight chains of n ≥ 1 interconnected mass points. The ground contact can be described either by non-symmetric dry friction or by unilateral differential constraints. The second part the paper deals with the peristaltic movement of a body due to a wavelike disturbance of the boundary surface. The investigations concentrate on motion in a tube or channel, and on motion on a horizontal plane as well. In both cases the body is modeled as a viscous Newton fluid. The dependence of the massflow through a cross section on disturbance and material data (viscosity, dimensions) is discussed. The paper presents first prototypes of technically implemented artificial worms.

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.

On Structure Preserving Transformations in Hamiltonian Control Systems

Hamiltonian control systems with natural output in the sense of [12] are consideredWe investigate statedependent co-ordinate transformations in the space of controls u and observables y which preserve the Hamiltonian structure.These transformations can be characterized and constructed by canonical transformations in the (y , u)-pace.The results generalize known statements on Hamiltonian systems affine in the control and hold for general gradient-like control systems as well.

Object contour reconstruction using bio-inspired sensors

This work is inspired and motivated by the sophisticated mammals sense organ of touch: vibrissa. Mammals, especially rodents, use their vibrissae, located in the snout region - mystacial vibrissae - to determine object contacts (passive mode) or to scan object surfaces (active mode). Here, we focus on the passive mode. In order to get hints for an artificial sensing prototype, we set up a mechanical model in form of a long slim beam which is one-sided clamped. We investigate in a purely analytical way a quasi-static sweep of the beam along a given profile, where we assume that the profile boundary is strictly convex. This sweeping procedure shows up in two phases, which have to be distinguished in profile contact with the tip and tangentially contact (between tip and base). The analysis eventuates in a phase decision criterion and in a formula for the contact point. These are the main results. Moreover, based on the observables of the problem, i.e. the clamping moment and the clamping forces, which are the only information the animal relies on, a reconstruction of the profile is possible - even with added uncertainty mimicking noise in experimental data.

Towards the Development of Tactile Sensors for Determination of Static Friction Coefficient to Surfaces

Natural vibrissae fulfill a lot of functions. Next to object distance detection and object shape recognition, the surface texture can be determined. Inspired by the natural process of surface texture detection, the goal is to adapt this feature by technical concepts. Modeling the vibrissa as an Euler–Bernoulli bending beam with a quasi-statically moving support and the vibrissa–surface contact with respect to Coulomb’s Law of Friction, a first approach was formed by the group of Behn and Steigenberger. Due to the motion of the support (pushing the vibrissa) and the surface contact, the vibrissa gets deformed. Firstly, the beam tip is sticking to the surface. The acting friction force prevents a movement of the beam tip until the maximal stiction is reached. The displacement of the support corresponds to changes in the acting forces and moments. Out of these changes the coefficient of static friction can be determined. The analytical results of Steigenberger and Behn are verified and validated by numerical simulations and an experiment.

Bio-inspired Technical Vibrissae for Quasi-static Profile Scanning

A passive vibrissa (whisker) is modeled as an elastic bending rod that interacts with a rigid obstacle in the plane. Aim is to determine the obstacle’s profile by one quasi-static sweep along the obstacle. To this end, the non-linear differential equations emerging from Bernoulli’s rod theory are solved analytically followed by numerical evaluation. This generates in a first step the support reactions, which represent the only observables an animal solely relies on. In a second step, these observables (possibly made noisy) are used for a reconstruction algorithm in solving initial-value problems which yield a series of contact points (discrete profile contour).

Stability of a disturbance decoupled rigid body

In this note, we investigate the stability behaviour of torque controlled rotating rigid bodies. The investigation is not only restricted to the angular velocity equations, but also includes the system describing the motion of the body-fixed frame. For the composite system we show that only orbital stability can occur.

Theoretical Investigations on the Behavior of Artificial Sensors for Surface Texture Detection

Animal vibrissae are used as natural inspiration for artificial tactile sensors, e.g., the mystacial vibrissae enable rodents to perform several tasks in using these tactile hairs: object shape determination and surface texture discrimination. Referring to the literature, the Kinetic Signature Hypothesis states that the surface texture detection is a highly dynamic process. It is assumed that the animals gather information about the surface texture out of a spatial, temporal pattern of kinetic events. This process has to be analyzed in detail to develop an artificial tactile sensor with similar functionalities. Hence, we set up a mechanical model for theoretical investigations of the process. This model is analyzed in two different directions using numerical simulations: at first a quasi-static and then a fully dynamic description.

Object Shape Recognition and Reconstruction Using Pivoted Tactile Sensors

Many mammals use some special tactile hairs, the so-called mystacial macrovibrissae, to acquire information about their environment. In doing so, rats and mice, e.g., are able to detect object distances, shapes, and surface textures. Inspired by the biological paradigm, we present a mechanical model for object contour scanning and shape reconstruction, considering a single vibrissa as a cylindrically shaped Euler-Bernoulli-bending rod, which is pivoted by a bearing. In doing so, we adapt our model for a rotational scanning movement, which is in contrast to many previous modeling approaches. Describing a single rotational quasi-static sweep of the vibrissa along a strict convex contour function using nonlinear Euler-Bernoulli theory, we end up in a boundary-value problem with some unknown parameters. In a first step, we use shooting methods in an algorithm to repeatedly solve this boundary-value problem (changing the vibrissa base angle) and generate the support reactions during a sweep along an object contour. Afterwards, we use these support reactions to reconstruct the object contour solving an initial-value problem. Finally, we extend the scanning process adding a second sweep of the vibrissa in opposite direction in order to enlarge the reconstructable area of the profile.