O. von Stryk

Modelling and Simulation of Electro‐ and Magnetorheological Fluid Dampers

Electro- and magnetorheological fluids are smart, synthetic fluids changing their viscosity from liquid to semi-solid state within milliseconds if a sufficiently strong electric or magnetic field is applied. When used in suitable devices, they offer the innovative potential of very fast, adaptively controllable interfaces between mechanical devices and electronic control units. This paper gives an overview on the basic properties of electro- and magnetorheological fluids and discusses various phenomenological models for whole devices and their applications. Numerical simulation results are presented for the passive suspension of a quarter vehicle model.

Towards Bipedal Jogging as a Natural Result of Optimizing Walking Speed for Passively Compliant Three-Segmented Legs

Elasticity in conventionally built walking robots is an undesired side-effect that is suppressed as much as possible because it makes control very hard and thus complex control algorithms must be used. The human motion apparatus, in contrast, shows a very high degree of flexibility with sufficient stability. In this research we investigate how compliance and damping can deliberately be used in humanoid robots to improve walking capabilities. A modular robot system consisting of rigid segments, joint modules and adjustable compliant cables spanning one or two joints is used to configure a human-like biped. In parallel, a simulation model of the robot was developed and analyzed. Walking motion is gained by oscillatory out-of-phase excitations of the hip joints. An optimization of the walking speed has been performed by improving the viscoelastic properties of the leg and identifying the appropriate hip control parameters. A good match was found between real robot experiments and numerical simulations. At higher speeds, transitions from walking to running are found in both the simulation as well as in the robot.

Efficient Walking Speed Optimization of a Humanoid Robot

The development of optimized motions of humanoid robots that guarantee fast and also stable walking is an important task, especially in the context of autonomous soccer-playing robots in RoboCup. We present a walking motion optimization approach for the humanoid robot prototype HR18 which is equipped with a low-dimensional parameterized walking trajectory generator, joint motor controller and an internal stabilization. The robot is included as hardware-in-the-loop to define a low-dimensional black-box optimization problem. In contrast to previously performed walking optimization approaches, we apply a sequential surrogate optimization approach using stochastic approximation of the underlying objective function and sequential quadratic programming to search for a fast and stable walking motion. This is done under the conditions that only a small number of physical walking experiments should have to be carried out during the online optimization process. For the identified walking motion for the considered 55 cm tall humanoid robot, we measured a forward walking speed of more than 30 cm s -1 . With a modified version of the robot, even more than 40 cm s -1 could be achieved in permanent operation.

Model-based off-line compensation of path deviation for industrial robots in milling applications

The scope of applications for industrial robots is limited in cases with strong forces at the end effector and high positioning and path accuracies required. Thus, their use in machining applications as a cost-saving, flexible alternative for machining tools is restricted due to mechanical compliance. A model-based off-line concept is presented to analyze, predict, and compensate the resulting path deviation of the robot under process force in milling applications. For this purpose a rigid multi-body dynamics model of the robot extended with additional joint elasticities and tilting effects is coupled with a material removal simulation providing the process forces. After systematically adjusting model parameters, an efficient simulation-based path correction strategy shows significant improvements of path accuracy. The general framework is applicable to any tree structured robots and allows for sensitivity analysis with respect to arbitrary model parameters.

Design and control of a robot for the assessment of psychological factors in prosthetic development

This paper introduces a robotic concept for the assessment of psychological factors in prosthetic design. Its aim is to imitate the postural movements of the participants while those are conducting squatting movements in order to investigate the integration of artificial limbs to the subjects body scheme. Therefore, the robot mimics the functionality and appearance of the human foot, shank and thigh as well as the ankle and knee joint. To induce a more realistic outer appearance, the hull of a shop-window mannequin is used as cladding. The robot is controlled by a computed torque control combined with a RGB-D sensor for the acquisition of the desired trajectories from the participant. In the test setup one leg of the participant is hidden from his view while the robot stands next to him and imitates the movements of this leg. This paper gives an insight in the theory of body schema integration. The concept of the robot is described and detailed information about the mechanical design and actuator dimensioning in accordance with psychological and biomechanical requirements are given. Furthermore, the concept of the human-machine interface, the control algorithm and simulations based on experimental data from a human subject are presented.

Research and development towards an autonomous biped walking robot

Methods for modeling, simulation and optimization of the dynamics, stability, and performance of humanoid robots are presented in this paper. Optimal control trajectory following by joint-level control combined with an online compensation method using Jacobians is proposed. The kinematic design, dynamic properties, hard- and software architecture for an autonomous biped, and experimental results are presented.

Design and Control Mechanisms for a 3 DOF Bionic Manipulator

Functionality and design of a bionic robot arm consisting of three joints driven by elastic and compliant actuators derived from biologically inspired principles are presented. In the first design standard springs with linear characteristics are utilized in combination with electrical drives. Different control approaches for the bionic robot arm are presented, discussed and evaluated by numerical simulations and experiments with regards to the long-term goal of a nature-like control performance

Prosthesis-User-in-the-Loop: A user-specific biomechanical modeling and simulation environment

In this paper, a novel biomechanical modeling and simulation environment with an emphasis on user-specific customization is presented. A modular modeling approach for multi-body systems allows a flexible extension by specific biomechanical modeling elements and enables an efficient application in dynamic simulation and optimization problems. A functional distribution of model description and model parameter data in combination with standardized interfaces enables a simple and reliable replacement or modification of specific functional components. The user-specific customization comprises the identification of anthropometric model parameters as well as the generation of a virtual three-dimensional character. The modeling and simulation environment is associated with Prosthesis-User-in-the-Loop, a hardware simulator concept for the design and optimization of lower limb prosthetic devices based on user experience and assessment. For a demonstration of the flexibility and capability of the modeling and simulation environment, an exemplary application in context of the hardware simulator is given.

Analysis of Industrial Robot Structure and Milling Process Interaction for Path Manipulation

Industrial robots are used in a great variety of applications for handling, welding, assembling and milling operations. Especially for machining operations, industrial robots represent a cost-saving and flexible alternative compared to standard machine tools. Reduced pose and path accuracy, especially under process force load due to the high mechanical compliance, restrict the use of industrial robots for machining applications with high accuracy requirements. In this chapter, a method is presented to predict and compensate path deviation of robots resulting from process forces. A process force simulation based on a material removal calculation is presented. Furthermore, a rigid multi-body dynamic system’s model of the robot is extended by joint elasticities and tilting effects, which are modeled by spring-damper-models at actuated and additional virtual axes. By coupling the removal simulation with the robot model the interaction of the milling process with the robot structure can be analyzed by evaluating the path deviation and surface structure. With the knowledge of interaction along the milling path a general model-based path correction strategy is introduced to significantly improve accuracy in milling operations.

The rubber hand illusion: Maintaining factors and a new perspective in rehabilitation and biomedical engineering?

Feelings of unrealistic body parts are related to deficits in human information processing and can occur as a part of phan, tom sensations after amputation [8]. Experimentally induced sensoric illusions like rubber hand illusion (RHI) [1] may help to understand basic information processing and could give new ideas for treatment or the rehabilitation pro, cess. Factors that are related to modulate sensoric illusions during movement may help to develop new intervention strategies in the rehabilitation of illusory symptoms. The goal of this study was to review the factors affecting persis, tence of the RHI effect during movement. We selected 13 keywords and searched in the following www.dimdi.de data bases (CCTR93, CDAR94, CDSR93, DAHTA, DAHTA, EA08, ED93, EM00, EM47, HG05, KP05, KR03, ME00, ME60, PI67, PY81, TV01, TVPP). A total of 160 articles were found. Duplicates were removed and the remaining list was filtered with the objective to explore the influence of active or passive movement during experimentally induced RHI. Then we identified six articles which experimentally examined persistence of RHI during active or passive move, ments. Results indicate that RHI are maintained during active or passive movements due to visual and temporal congru, ency. During active movements the RHI is more stable or global than in passive movements or during tactile stimulation. Factores like visual and temporal congruency are related to maintain RHI and are discussed in the rehabilitation of phan, tom sensations regarding new innovations in the design of prosthetics