Martin Friedmann

Adequate motion simulation and collision detection for soccer playing humanoid robots

In this paper a humanoid robot simulator based on the multi-robot simulation framework (MuRoSimF) is presented. Among the unique features of this simulator is the scalability in the level of physical detail in both the robots motion and sensing systems. It facilitates the development of control software for humanoid robots which is demonstrated for several scenarios from the RoboCup Humanoid Robot League. Different requirements exist for a humanoid robot simulator. E.g., testing of algorithms for motion control and postural stability require high fidelity of physical motion properties whereas testing of behavior control and role distribution for a robot team requires only a moderate level of detail for real-time simulation of multiple robots. To meet such very different requirements often different simulators are used which makes it necessary to model a robot multiple times and to integrate different simulations with high-level robot control software. MuRoSimF provides the capability of exchanging the simulation algorithms used for each robot transparently, thus allowing a trade-off between computational performance and fidelity of the simulation. It is therefore possible to choose different simulation algorithms which are adequate for the needs of a given simulation experiment, for example, motion simulation of humanoid robots based on kinematical, simplified dynamics or full multi-body system dynamics algorithms. In this paper also the sensor simulation capabilities of MuRoSimF are revised. The methods for motion simulation and collision detection and handling are presented in detail including an algorithm which allows the real-time simulation of the full dynamics of a 21 DOF humanoid robot. Merits and drawbacks of the different algorithms are discussed in the light of different simulation purposes. The simulator performance is measured and illustrated in various examples, including comparison with experiments of a physical humanoid robot.

Modular software architecture for teams of cooperating, heterogeneous robots

For teams of cooperating autonomous lightweight robots with challenging dynamical locomotion properties a platform independent modular software architecture and platform independent modules for sensor data processing, planning and motion control have been developed. The software architecture allows high level communication between modules on different abstraction levels of the control architecture within one robot system as well as communication between different and heterogeneous robots and computers using wireless network. Very different behavior control paradigms may be realized on the basis of the developed architecture. The application to teams of cooperating small and medium size humanoid robots is investigated in this paper. Scenarios for inter robot communication and cooperative task accomplishment are described.

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.

Multilevel Testing of Control Software for Teams of Autonomous Mobile Robots

Developing control software for teams of autonomous mobile robots is a challenging task, which can be facilitated using frameworks with ready to use components. But testing and debugging the resulting system as teached in modern software engineering to be free of errors and tolerant to sensor noise in a real world scenario is to a large extend beyond the scope of current approaches. In this paper multilevel testing strategies using the developed frameworks RoboFrame and MuRoSimF are presented. Testing incorporating automated tests, online and offline analysis and software-in-the-loop (SIL) tests in combination with real robot hardware or an adequate simulation are highly facilitated by the two frameworks. Thus the efficiency of validation of complex real world applications is improved. In this way potential errors can be identified early in the development process and error situations in real world operations can be reduced significantly.

Reusable architecture and tools for teams of lightweight heterogeneous robots

The software framework RoboFrame has been designed to meet the special requirements for teams of lightweight autonomous heterogeneous robot systems. Due to platform abstraction and modern object oriented design, it allows the reuse of components of common robot control software. It can also efficiently be implemented on new platforms and enables different control architectures for different tasks. For the exemplary application in autonomous robot soccer teams configurable and portable algorithms for vision, world modeling, behavior and motion control have been developed on top of the framework. For debugging, controlling and monitoring, an extendable graphical user interface and a generic simulator package have been implemented around the framework. Based on these instruments, different applications for homogeneous and heterogeneous robot teams can be realized in short time.

Tailored Real-Time Simulation for Teams of Humanoid Robots

Developing and testing the key modules of autonomous humanoid robots (e.g., for vision, localization, and behavior control) in software-in-the-loop (SIL) experiments, requires real-time simulation of the main motion and sensing properties. These include humanoid robot kinematics and dynamics, the interaction with the environment, and sensor simulation. To deal with an increasing number of robots per team the simulation algorithms must be very efficient. In this paper, the simulator framework MuRoSimF (Multi-Robot-Simulation-Framework) is presented which allows the flexible and transparent integration of different simulation algorithms with the same robot model. These include several algorithms for simulation of humanoid robot motion kinematics and dynamics (with O(n) runtime complexity), collision handling, and camera simulation including lens distortion. A simulator for teams of humanoid robots based on MuRoSimF is presented. A unique feature of this simulator is the scalability of the level of detail and complexity which can be chosen individually for each simulated robot and tailored to the requirements of a specific SIL test. Performance measurements are given for real-time simulation on a moderate laptop computer of up to six humanoid robots with 21 degrees of freedom, each equipped with an articulated camera.

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.

Simulation of Multi-Robot Teams with Flexible Level of Detail

A device for detecting the actual position of an elevator car using a computer has an interfloor detector 5 which detects the elevator car passing through an intermediate zone between adjacent landing floors, and a floor level detector 6 which detects when the elevator car is located at a landing floor. A position detecting device which is fed output signals from the two detectors precisely memorizes the actual position of the elevator car.

Towards the deployment of industrial robots as measurement instruments - An extended forward kinematic model incorporating geometric and nongeometric effects

In the area of mounting and spot-welding of body-in-white, absolutely accurate robots are installed as measuring instruments, replacing expensive coordinate and other external measuring machines. Measurement technologies based on industrial robots play an increasingly important role. Such applications require highly accurate robots. Prior to deployment of highly accurate robot, however, it needs to be ensured that the implemented robot model fits the real model. Robot calibration can offer a significant opportunity to improve the positioning accuracy and to cut production costs. Existing calibration approaches fail to capture geometric and elastic effects occurring in the robot forward kinematics. Therefore, in this work an extended forward kinematic model incorporating both geometric and elastic effects has been developed in which the positioning accuracy of a manipulator, with or without an accurate internal robot model in the robot controller, is improved.

A New, Open and Modular Platform for Research in Autonomous Four-Legged Robots

In this paper the design goals for a new, open and modular, four-legged robot platform are described that was developed in reaction to the open call for a standard platform issued by the RoboCup Federation in 2006. The new robot should have similar motion and sensing capabilities like the previously used Sony AIBO plus several new ones. The hardware and software should be open, modular and reconfigurable. The robot should be resonably priced and allow annually upgrades.