Philipp Miermeister

IPAnema: A family of Cable-Driven Parallel Robots for Industrial Applications

Nowadays there are very little robot systems in operation in the field of medium to large-scale handling and assembly mostly due to lack of repetitive processes or shortcomings in programming and configuring such robots. In this paper we introduce a family of cable-driven parallel robot called IPAnema that are designed for industrial processes. We address the system architecture, key components such as winches and controller, as well as design tools. Furthermore, some experimental data from the evaluation are presented to illustrate the performance of cable robots.

An Elastic Cable Model for Cable-Driven Parallel Robots Including Hysteresis Effects

Experimental results indicate that time invariant linear elastic models for cable-driven parallel robots show a significant error in the force prediction during operation. This paper proposes the use of an extended model for polymer cables which allows to regard the hysteresis effects depending on the excitation amplitude, frequency, and initial tension level. The experimental design as well as the parameter identification are regarded.

Auto Calibration Method for Cable-Driven Parallel Robots Using Force Sensors

This paper presents an auto calibration method for overconstrained cable-driven parallel robots using internal position and force sensors. The consideration of cable forces is necessary in order to regard the cable elasticity. A calibration workflow is proposed and implemented including pose selection, measurement, and parameter adjustment. The calibration procedure is not limited to the geometrical parameters, but also allows to identify force related parameters such as the cable stiffness and platform mass. The calibration results are shown for an unknown parameter set and the influence of sensor noise on the calibration results is presented.

Modelling and Real-Time Dynamic Simulation of the Cable-Driven Parallel Robot IPAnema

In this paper, the mechatronic model of the cable-driven parallel robot IPAnema ispresented. The dynamic equations are established including the dynamic behavior of the mobileplatform, the pulley kinematics of the winches, and a cable model based on linear springs. Themodel of the actuation systems consists of the electro-dynamic behavior of the power train as wellas the dynamics of the servo controller. The presented model is feasible for real-time simulation,controller design, as well as case studies for high-dynamic or large-scale robots. Simulation resultsand experimental measurements with the cable-driven parallel robot IPAnema are presented andcompared

Design of Cable-Driven Parallel Robots with Multiple Platforms and Endless Rotating Axes

Cable-driven parallel robots allow high performance operation due to their minimal actuated system mass. In order to deal with more complex handling operations it is desirable to have an additional actuated serial kinematics on the platform. This usually comes along with the problem of extra weight and energy supply for the motors on the platform. In this paper we present a new approach to the problem by introducing a hybrid design with coupled platforms and cable-driven serial kinematics. Especially the concept of an endless rotatable axis will be highlighted.

Cable-driven parallel robots for industrial applications: The IPAnema system family

Nowadays there are very little robot systems in operation in the field of medium to large-scale handling and assembly mostly due to lack of repetitive processes or shortcomings in programming and configuring such robots. In this paper we introduce a family of cable-driven parallel robot called IPAnema that are designed for industrial processes. We address the system architecture, key components such as winches and controller, as well as design tools. Furthermore, some experimental data from the evaluation are presented to illustrate the performance of cable robots.

Fluorescence-based in situ assay to probe the viability and growth kinetics of surface-adhering and suspended recombinant bacteria

Bacterial adhesion and biofilm growth can cause severe biomaterial-related infections and failure of medical implants. To assess the antifouling properties of engineered coatings, advanced approaches are needed for in situ monitoring of bacterial viability and growth kinetics as the bacteria colonize a surface. Here, we present an optimized protocol for optical real-time quantification of bacterial viability. To stain living bacteria, we replaced the commonly used fluorescent dye SYTO® 9 with endogenously expressed eGFP, as SYTO® 9 inhibited bacterial growth. With the addition of nontoxic concentrations of propidium iodide (PI) to the culture medium, the fraction of live and dead bacteria could be continuously monitored by fluorescence microscopy as demonstrated here using GFP expressing Escherichia coli as model organism. The viability of bacteria was thereby monitored on untreated and bioactive dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DMOAC)-coated glass substrates over several hours. Pre-adsorption of the antimicrobial surfaces with serum proteins, which mimics typical protein adsorption to biomaterial surfaces upon contact with host body fluids, completely blocked the antimicrobial activity of the DMOAC surfaces as we observed the recovery of bacterial growth. Hence, this optimized eGFP/PI viability assay provides a protocol for unperturbed in situ monitoring of bacterial viability and colonization on engineered biomaterial surfaces with single-bacteria sensitivity under physiologically relevant conditions.

Differential Kinematics for Calibration, System Investigation, and Force Based Forward Kinematics of Cable-Driven Parallel Robots

In this paper the differential kinematics for cable-driven robots is derived and the use for calibration, system investigation and a force based forward kinematics is shown. The Jacobians for each part of the kinematic chain are derived with respect to the platform pose and the most important system parameters. Beside the consideration of geometrical quantities, the differential relations between non-geometrical quantities such as cable stiffness and cable forces are determined. The decomposition in the most fundamental Jacobians allows to analyse and compute more complex relations by reassembling the Jacobians as needed. This approach allows more insight in the system behavior and enables the reuse of the individual modules. The purpose of this paper is to provide the framework and the key equations and to show the use for calibration, force based forward kinematics and system analysis as well as for control purposes.

Workspace and Interference Analysis of Cable-Driven Parallel Robots with an Unlimited Rotation Axis

A drawback of many cable-driven parallel robots is a relatively small orientation workspace. In this paper, two design variants for cable-driven parallel robots with nine and twelve cables are proposed that allow for large rotations. It is shown that the platform can perform a 360(^{circ }) rotation while maintaining positive tension in all cables and without collisions amongst the cables. Furthermore, workspace studies of the total orientation workspace are provided. Surprisingly, this family of cable robot is capable to perform an unlimited rotation within a translational workspace of reasonable size. Finally, the efficiency and computation time of force distribution algorithms is compared for cable robots having twelve cables.

Investigation of the Influence of Elastic Cables on the Force Distribution of a Parallel Cable-Driven Robot

Cable-driven parallel robots rely on cables instead of rigid links to manipulate the endeffector in the workspace. The cable force distribution is the result of cable elongation and the force coupling at the endeffector. In this paper, the experimental investigation of the force coupling is presented. In the experiment, the cable length in each individual cable was varied, and the resulting progression of the force distribution and the deflection were measured. With this approach, the steady state gain matrix for the transfer function between a delta in cable length and the resulting changes in the cables forces can be determined. Furthermore, the impact of the observed force coupling on cable force control is discussed.