Andreas Mueller

Andreas Mueller
Johannes Kepler University Linz | JKU · Institute of Robotics

Prof. Dr.-Ing. habil

About

334
Publications
79,218
Reads
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2,391
Citations
Additional affiliations
September 2014 - present
Johannes Kepler University Linz
Position
  • Professor (Full)
September 2013 - present
Independent Researcher
Position
  • Professor (Associate)
January 2012 - August 2013
Institute of Mechatronics
Position
  • Deputy Manager
Description
  • www.ifm-chemnitz.de

Publications

Publications (334)
Article
Full-text available
It is commonly assumed that the singularities of kinematic mappings constitute generically smooth manifolds but this has not yet been proven. Moreover, before this assumption can be verified, the concept of genericity needs to be clarified. In this paper, two different notions of generic properties of kinematic mappings are discussed. One accounts...
Article
Full-text available
The basis for any model-based control of dynamical systems is a numerically efficient formulation of the motion equations, preferably expressed in terms of a minimal set of independent coordinates. To this end the coordinates of a constrained system are commonly split into a set of dependent and independent ones. The drawback of such coordinate pa...
Article
Full-text available
Redundant actuation of parallel manipulators can lead to internal forces without generating end-effector forces (preload). Preload can be controlled in order to prevent backlash during the manipulator motion. Such control is based on the inverse dynamics. The general solution of the inverse dynamics of redundantly actuated parallel manipulators is...
Article
This paper presents the kinematics about the center of mass (CoM) for robotic mechanisms based on Lie Group theory because the movements of CoM is very important for mobile manipulating robots. Different from general kinematics, the CoM kinematics relates the position of the CoM to the joint angles and the pose of the robot. The concept of the homo...
Presentation
Full-text available
Slides of the talk to the paper 'On the Use of Ternary Products to Characterize the Dexterity of Spatial Kinematic Chains'
Article
A consistent method is presented for solving the so-called general waiter problem, which is to move a tray (mounted at the end-effector of a robot) with a number of loosely placed objects (e.g. cups) as fast as possible such that the objects do not slide at any time. The geometric path of the tray motion is prescribed while the attitude of the tray...
Article
Robotic surface treatment is already broadly used in the manufacturing industry because it guarantees repeatable high-quality surfaces at short production time. Such a robotic solution, with an accurate control of the applied force on a surface, requires a robot that is either equipped with a force/torque sensor or, alternatively, with a force comp...
Chapter
Reconfigurable architecture is a disruptive concept with unique opportunities for creativity in design towards more usable buildings, better energy efficiency and improved comfort for the occupants. From an engineering perspective, implementations involve mechanism design and control, while analytical approaches from robotics become relevant. A str...
Article
Full-text available
This paper presents a method of optimizing the design of robotic manipulators using a novel kinematic model pruning technique. The optimization departs from an predefined candidate linkage consisting of a initial topology and geometry. It allows simultaneously optimizing the degree of freedom, the link lengths and other kinematic or dynamic perform...
Article
Identifying dynamic parameters of an elastic robotic system can be a quite challenging task. This is because elastic robotic systems are often highly underactuated and sensor data may only be available for the driven states. To overcome this shortcoming, the identification process can be addressed by different experiments based on different reduced...
Article
Parallel manipulators, also called parallel kinematics machines (PKM), enable robotic solutions for highly dynamic handling and machining applications. The safe and accurate design and control necessitates high-fidelity dynamics models. Such modeling approaches have already been presented for PKM with simple limbs (i.e. each limb is a serial kinema...
Chapter
The characterization of the workspace for general spatial 3R chains with skew joint axes is refined by describing the variety of singular displacements as the union of the singular configuration manifolds of orientation type, position type, and attitude type. The surface of attitude singularities is revealed by transferring the singularity sets of...
Chapter
Full-text available
The inverse kinematics problem is ill-posed near kinematic singularities leading to extremely large joint velocities. This classical problem is addressed from a different perspective; instead of prescribing the end-effector (EE) motion in terms of a path parameter, the motion is parameterized in terms of the arc length in joint space. This allows t...
Chapter
Full-text available
Two performance indices are introduced that characterize the singularities and the manipulability of a general spatial kinematic chain in a threefold, physically significant manner. The ternary volume and shape indices are obtained as characteristic scalars of two ternary product matrices that capture the geometry of the joint axes in a certain con...
Chapter
In this paper, a methodology to generate realistic gait patterns is presented. Human gait motion capture data is used along with a kinematic model of the human lower extremity to derive a parametric and time-continuous analytical description of the walking motion. This allows for reproduction of individual recorded gait cycles and for generating ne...
Article
A classical approach to the MBS modeling is to use absolute coordinates, i.e. a set of (possibly redundant) coordinates that describe the absolute position and orientation of the individual bodies w.r.t. to an inertial frame (IFR). A well-known problem for the time integration of the equations of motion (EOM) is the lack of a singularity-free param...
Article
Full-text available
Derivatives of equations of motion (EOM) describing the dynamics of rigid body systems are becoming increasingly relevant for the robotics community and find many applications in design and control of robotic systems. Controlling robots, and multibody systems comprising elastic components in particular, not only requires smooth trajectories but als...
Data
Corrections to the published article
Preprint
Full-text available
The characterization of the workspace for general spatial 3R chains with skew joint axes is refined by describing the variety of singular displacements as the union of the singular configuration manifolds of orientation type, position type, and attitude type. The surface of attitude singularities is revealed by transferring the singularity sets of...
Presentation
Full-text available
The characterization of the workspace for general spatial 3R chains with skew joint axes is refined by describing the variety of singular displacements as the union of the singular configuration manifolds of orientation type, position type, and attitude type. The surface of attitude singularities is revealed by transferring the singularity sets of...
Article
Full-text available
The exponential and Cayley maps on SE(3) are the prevailing coordinate maps used in Lie group integration schemes for rigid body and flexible body systems. Such geometric integrators are the Munthe–Kaas and generalized- α schemes, which involve the differential and its directional derivative of the respective coordinate map. Relevant closed form ex...
Poster
Full-text available
The inquest of spatial motions of rigid bodies is a classic topic in mechanism science and an ongoing activity that is relevant, amongst others, for planning and real-time control of robotic systems. This document describes the concept for a poster contribution to the RSS workshop Geometry and Topology in Robotics: Learning, Optimization, Planning,...
Article
Full-text available
Hippotherapy, riding a horse in the context of rehabilitation, is a medical treatment that successfully has been employed in various fields, e.g. for improving locomotion performance of patients with movement disorders. Robotic systems enable the application of hippotherapy in clinical environments with additional benefits, like adjustable speed an...
Chapter
Nowadays, automatized surface treatment via robots is already common in the manufacturing industry and such robotic solutions require accurate and reliable force control for high-quality surfaces. However, no standardized test for the quality assessment of robot force control exists yet. By comparison, the ISO 9283 test is used for the evaluation o...
Article
Full-text available
Robotic manipulators physically interacting with their environment must be able to measure contact forces/torques. The standard approach to this end is attaching force/torque sensors directly at the end-effector (EE). This provides accurate measurements, but at a significant cost. Indirect measurement of the EE-loads by means of torque sensors at t...
Article
Full-text available
The Boltzmann–Hamel (BH) equations are central in the dynamics and control of nonholonomic systems described in terms of quasi-velocities. The rigid body is a classical example of such systems, and it is well-known that the BH-equations are the Newton–Euler (NE) equations when described in terms of rigid body twists as quasi-velocities. It is furth...
Article
Pseudo-omnidirectional vehicles (POV) are equipped with several center steered and driven standard wheels, and exhibit high maneuverability and positioning accuracy. Yet this class of mobile systems is rarely considered. Despite their simple setup, the mathematical modeling is challenging. Moreover all models presented so far suffer from artificial...
Preprint
Full-text available
Derivatives of equations of motion describing the rigid body dynamics are becoming increasingly relevant for the robotics community and find many applications in design and control of robotic systems. Controlling robots, and multibody systems comprising elastic components in particular, not only requires smooth trajectories but also the time deriva...
Article
The local analysis is an established approach to the study of singularities and mobility of linkages. Key result of such analyses is a local picture of the finite motion through a configuration. This reveals the finite mobility at that point and the tangents to smooth motion curves. It does, however, not immediately allow to distinguish between mot...
Chapter
Full-text available
This paper revisits a three-loop spatial linkage that was proposed in an ARK 2004 paper by Karl Wohlhart (as extension of a two-loop linkage proposed by Eddie Baker in 1980) and later analyzed in an ARK 2006 paper by Diez-Martínez et al. A local analysis shows that this linkage has a finite degree of freedom (DOF) 3 (and is thus overconstrained) wh...
Chapter
Based on the idea of variable stiffness mechanisms, a variety of such mechanisms is shown in this work. Specifically, 2-DOF parallel kinematic machines equipped with redundant actuators and non-linear springs in the actuated joints are presented and a comparative overview is drawn. Accordingly, a general stiffness formulation in task space of all m...
Article
Full-text available
Dynamic balance eliminates the fluctuating reaction forces and moments induced by high-speed robots that would otherwise cause undesired base vibrations, noise and accuracy loss. Many balancing procedures, such as the addition of counter-rotating inertia wheels, increase the complexity and motor torques. There exist, however, a small set of closed-...
Article
Optimal control in general, and flatness-based control in particular, of robotic arms necessitate to compute the first and second time derivatives of the joint torques/forces required to achieve a desired motion. In view of the required computational efficiency, recursive $O(n)$ -algorithms were proposed to this end. Aiming at compact yet efficie...
Chapter
The modeling of parallel kinematic machines (PKM) has been a topic of ongoing research since PKM started to gain popularity more than twenty years ago. Due to the modular setup of most PKM, research has been conducted towards modular modeling paradigms. This applies in particular to so-called fully parallel PKM. Recently, a general modeling approac...
Conference Paper
The local analysis is an established approach to the study of singularities and mobility of linkages. Key result of such analyses is a local picture of the finite motion through a configuration. This reveals the finite mobility at that point and the tangents to smooth motion curves. It does, however, not immediately allow to distinguish between mot...
Article
Full-text available
The analysis of human movements rests on a realistic human body model. Deducing model parameters from anthropomorphic data is challenging since these are inherently imprecise. An approach to improve model accuracy is the parameter adaptation based on motion data. 3D motion capture data are already being used for generating the trajectories of a hum...
Conference Paper
Full-text available
This paper presents several point-to-point optimization tasks of humanoid arm motions. The focus lies on optimization of elementary arm motions. Several cost functions for optimization tasks are defined. Tasks in respect of time optimal control, minimizing joint loads and maximizing the vertical torque of the torso are presented. The dynamic optima...
Chapter
Full-text available
According to the ISO/TS 15066, human safety in quasi-static impact situations in human-robot collaboration is assessed first by identifying all high-risk impact situations and then by measuring maximal and steady-state values the impact force and pressure at these possibly critical situations. This means that if something is changed in a collaborat...
Article
Immobile linkages admitting only (possibly higher-order) infinitesimal mobility which does not extend to finite motions are shaky structures. In the past, the determination of the order of mobility or shakiness was usually approached in a purely kinematic way namely the higher order kinematic constraint analysis, which involves the solutions of the...
Chapter
The field of sound event detection is a growing sector which has mainly focused on the identification of sound classes from daily life situations. In most cases these sound detection models are trained on publicly available sound databases, up to now, however, they do not include acoustic data from manufacturing environments. Within manufacturing i...
Article
Full-text available
Dynamics modeling is indispensable for the design and control of dexterous parallel manipulators (PKM). The various modeling approaches proposed in the literature build upon the classical formulations for serial manipulators, and thus inherit those modeling conventions that tend to be restrictive rather then user-friendly. Moreover, the special kin...
Article
Full-text available
Parallel mechanisms are used increasingly often as modular subsystem units in various robots and man-machine interfaces for their superior stiffness, payload-to-weight ratio and dynamic properties. This leads to series-parallel hybrid robotic systems which utilize closed loop linkages and parallel kinematic machines as an abstraction of a certain k...
Article
Process control in manufacturing industries usually lacks flexibility and adaptability. The process planning is traditionally pursued within the production scheduling, and then remains unchanged until a major overhaul is necessary. Consequently, no process knowledge acquired by the machine operators is used to adapt, and thus improve, the process c...
Preprint
Full-text available
The branches of motion in the configuration space of a reconfigurable linkage can intersect in different ways leading to different types of singularities. In the vast majority of reported linkages whose configuration spaces contain multiple branches of motion the intersection happens transversally, allowing local methods , like the computation of i...
Article
Cooperative grasping refers to the situation when an object is manipulated by multiple robots and the grasp is achieved by the unilateral contact between the robots and the object. This is different from the cooperation of multiple robots where each robot rigidly grasps the object. Motion planning of cooperative grasping tasks involves active force...
Article
Full-text available
Parallel mechanisms are increasingly being used as modular subsystem units in various robots and man-machine interfaces for their superior stiffness, payload-to-weight ratio and dynamic properties. This leads to series-parallel hybrid robotic systems which are challenging to model and control due to the presence of various closed loops. Most model...
Chapter
Full-text available
A robot is a flexible tool and handling device. However, by eliminating safety fences in robotic applications, flexibility is limited as regulations on personal safety must be followed. Any modification on the system or application will require a new risk assessment before the system can be put back into operation. This circumstance costs time and...
Chapter
Due to their deterministic behaviour, compliant mechanisms are well-suited for high-precision applications. In this paper the benefits of redundant links and actuation are investigated in terms of increasing support stiffness and homogenising actuator loads.
Chapter
Lightweight robots with flexible links are perfect candidates for applications which require contact with the environment due to their inherited compliance. However, due to the lower stiffness compared to typical industrial robots it is imperative to handle occurring link vibrations. This can be done with different vibration damping control approac...
Article
A consistent method is presented for solving the so-called general waiter problem, which resembles the general task of manipulating several objects that are loosely placed on a robot, rather than grasped or fixed otherwise. The waiter problem consists of moving a tray (mounted at the end-effector of a robot) with a number of cups, from one pose to...
Article
Time/energy optimal trajectory planning for a Segway model (inverted pendulum on two independently actuated wheels) is addressed. Basis for this planning is the dynamical model for this under-actuated, non-holonomic multibody system. In order to reduce the calculation effort for the optimization, an input/output transformation is applied, which lea...
Article
Traditionally, the calibration of robots is pursued either using model-based or model-free methods. Only a few attempts to combine both approaches were reported, particularly the combination of geometric calibration and artificial neural network (ANN). The latter was mostly used to compensate the positioning error, however. This paper introduces an...
Article
In process automation of logistic systems autonomous mobile platforms play an important role with high demands on flexibility and maneuverability. Limited space can be a restriction for non-omnidirectional vehicles. In this paper a quasi-omnidirectional platform is considered which can switch between four different motion-modes: wheel alignment in...
Conference Paper
Full-text available
It is becoming increasingly popular to use parallel mechanisms as modular subsystem units in the design of various robots for their superior stiffness, payload-to-weight ratio and dynamic properties. This leads to series-parallel hybrid robotic systems which pose several challenges in their modeling and control e.g. resolution of loop closure const...
Article
Full-text available
This contribution focuses on the optimal trajectory planning for a Segway model (inverted pendulum on two independently actuated wheels). Basis for this planning is the dynamical model for this under‐actuated, non‐holonomic multibody system. For the stabilization as well as the trajectory control, a partial input/output linearization is performed,...
Article
Full-text available
Impact and the resulting contact forces can be determined by dynamic simulation once a validated model for the robot and of the contact area of the human is available. Methods for the identification of relevant geometric and dynamic parameters of the robot model are well established. While the experimental validation of constitutive models for huma...
Article
Full-text available
The motions of mechanisms can be described in terms of screw coordinates by means of an exponential mapping. The product of exponentials (POE) describes the configuration of a chain of bodies connected by lower pair joints. The kinematics is thus given in terms of joint screws. The POE serves to express loop constraints for mechanisms as well as th...
Conference Paper
Full-text available
Parallel mechanisms are increasingly being used as modular subsystem units in various robots and man-machine interfaces for their superior stiffness, payload-to-weight ratio and dynamic properties. This leads to series-parallel hybrid robotic systems which are difficult to model and control due to the presence of various closed loops. Most model ba...
Conference Paper
It has become obvious that certain singular phenomena cannot be explained by a mere investigation of the configuration space, defined as the solution set of the loop closure equations. For example, it was observed that a particular 6R linkage, constructed by combination of two Goldberg 5R linkages, exhibits kinematic singularities at a smooth point...
Conference Paper
Full-text available
Parallel kinematics manupulators (PKM) are established robotic systems. Yet there is no established modeling approach that takes into account the special kinematics of the (usually structurally identical) limbs. In this paper a modeling approach is proposed that accounts for the special kinematics and topology of PKM. It makes use of modern Lie gro...
Article
Full-text available
A structural concept for reconfigurable buildings is considered. Its basic element is the planar n-bar linkage whose joints are equipped with brakes. Stepwise reconfigurations are realized based on the ‘effective 4-bar’ method. During each intermediate step (n-4) joints of the mechanism are selectively locked reducing the system to a 1-DOF mechanis...
Chapter
Full-text available
The configuration space of most of the reported kinematotropic mechanisms consists of several subvarieties whose dimension varies between two values. Therefore, most of the reported kinematotropic mechanisms can change their number of degrees of freedom between two values only. In this paper a fully parallel mechanism is presented which has a confi...
Chapter
It is crucial to determine the mobility in regular and singular configurations of a mechanism. At a configuration space singularity, a mechanism can branch between different motion modes. All reported approaches to the local mobility analysis aim to identify possible finite motions, more precisely tangents to these motions. The latter is formalized...
Preprint
It has become obvious that certain singular phenomena cannot be explained by a mere investigation of the configuration space, defined as the solution set of the loop closure equations. For example, it was observed that a particular 6R linkage, constructed by a combination of two Goldberg 5R linkages, exhibits kinematic singularities at a smooth poi...
Chapter
Correct mobile robot localization requires precise knowledge of the robot’s pose in plane, i.e. the Cartesian x and y coordinates and yaw angle \( \theta \). Mobile robot pose information estimated from on-board odmetry sensors is not fully trusted and it suffers from unceratinties exerted by the robot incorporated with actuators nonlinearities and...
Article
A novel optimization algorithm for the calibration of redundantly actuated parallel manipulator (RA-PKM) is presented. The method uses an analytical indicator function (IF) which takes a specific value at the motion reversal points (MRP). MRP are configurations where the speed of one passive actuator vanishes during a continuous motion. IF depends...