Dynamics simulation is a valuable tool for biped robot hardware and controller design. Due to the complexity of biped walking robots, simulation times can be quite high. It is therefore important to identify the key components in modeling the system so that the phenomena of interest can be correctly predicted at a reasonable numerical cost. In this paper a detailed and a reduced simulation of the biped robot JOHNNIE are presented and results are compared with experimental data. The comparison shows that results for both models correctly predict global dynamics of the system, while some phenomena are only captured by the more complex model

The paper presents the performance enhanced humanoid robot LOLA which is currently being manufactured. The goal of the project is the realization of a fast, human-like walking motion. The robot is characterized by its lightweight construction, a modular, multi-sensory joint design with brushless motors and an electronics architecture using decentralized joint controllers. The fusion of motor, gear and sensors into a highly integrated, mechatronic joint module has several advantages for the whole system, including high power density, good dynamic performance and reliability. Additional degrees of freedom are introduced in elbow, waist and toes. Linear actuators are employed for the knee joints for a better mass distribution in the legs

The biped robot "Johnnie" is designed to achieve a dynamically stable gait pattern, allowing for high walking velocities. Besides accurate and fast sensors, a powerful computer system is essential for the performance and stability of the machine. The control system requires hard real-time capabilities and low cycle times. With our new control concept and the new computer system, walking speeds of 2.4 km/h have been achieved in experiments.

The biped robot "Johnnie" is designed to achieve a dynamically stable gait pattern, allowing for high walking velocities. Very accurate and fast sensors were developed for the machine. In particular the design of the 3D-orientation sensor and the 6-axes force-torque sensor are presented. The control scheme is based on the information from these sensors to deal with unstructured terrain and disturbances. Two different implementations are investigated: a computed torque approach and a trajectory control with adaptive trajectories. Walking speeds of 2.0 km/h have been achieved in experiments.

Functional electrical stimulation (FES) is a suitable method for the therapy of hemiparetic walking. However, FES requires suitable human and muscle models in order to achieve fast improvements of the patient's gait. Furthermore, an intelligent control scheme is to be employed considering the patient's autonomous motor activity. This paper presents the general therapeutic approach to therapy the hemiparetic gait. Further, human body and muscle models are presented and control algorithm are proposed. Concluding results from simulations and experiments are presented and debated.

This paper deals with the further development of the tube crawling robot "MORITZ", which was built at the Technical University of Munich. This robot can climb through pipes of different inclinations. It is improved in the recent research project, so that it also can manage tube junctions. After a brief introduction about problems concerning such a robot the used gait pattern is explained. Additionally some simulation results-showing the load at the robot during a motion through a tube crossing-are presented. Moreover the new developed joints in the central body as well as the sensors are described. The paper ends with a brief description of the crawler's control and its modifications for the new climbing maneuver in tube crossings.

Within the large variety of existing and still newly emerging biped walking machines Jogging JOHNNIE represents a fundamental study on fast walking and on especially adapted foot-dynamics. Air phases are possible with two feet lifted off the ground. Each foot possesses six degrees of freedom with respect to the body and additionally seven degrees of freedom within the local foot environment. The overall system includes 23 degrees of freedom. It is 1.80 m, large and weighs 40 kg. Up to now stable walking has been achieved.

Deals with the design and control of an anthropomorphic autonomous biped robot. The objective is to realize a dynamically stable, three-dimensional walking and jogging motion. The design, sensors and electronics of the robot are introduced. Particular emphasis has been devoted to achieving a high power-to-weight ratio. The corresponding methods for weight reduction are presented. The control scheme is discussed. It is based on the method of feedback linearization employing the equations of motion of the system.

The project of a two-legged walking robot is presented. The control system is based on a nonlinear control scheme using the method of feedback linearization. Special effort has been devoted to the trajectory generation which is computed such that the system remains controllable throughout the entire gait cycle. The controller and simulation algorithm have been implemented parametrically. Parameter studies have been performed which lead to the final design. The mechanical design with particular emphasis on actuators and sensors is presented.

In realizing walking machines friction plays an important role which cannot be neglected. Friction will be generated in contacts of the feet with the ground and in drives including gears. Friction influences the power budget and thus the selection of motors, and it influences significantly the control concepts. The paper gives a general description of friction and a walking machine example.

Deals with TELBOT, a telerobot with a special kinematic design. Due to its lightweight construction, an elastic multibody model of this robot is presented. Reduced to a rigid model for online computation, this model is implemented in a model based controller suitable for telerobots, where the trajectories are usually unknown a priori. The model also enables an optimization of the control coefficients of a conventional PID controller considering arbitrary cost functions. Simulation results are compared to measurements to verify the approach.

We present an approach to compensate for discrete contact state errors in regrasping tasks with multi-fingered robotic hands. An adaptation of reference trajectories connected with a hybrid discrete continuous control architecture allows stable grasps even if moving fingers cannot contact at the desired position on a grasped object. We propose a robust control setup that allows multiple regrasping tasks of objects to be performed using this compensation strategy and contact force optimization. Experimental results with the hydraulic robotic hand of the TUM verify the proposed approach and illustrate the increase in robustness for multi-fingered manipulation.

In robotic manipulation the interaction between robot and environment is an essential part of the task. In order to deal with impacts, friction and constrained motion, a model-based optimization approach is suggested which relies on a detailed dynamic model of the manipulator itself, the process dynamics of the task and the interactions between those two. These models are used to define an optimization problem, which is then solved using numerical programming methods. It is illustrated with an assembly task, namely mating a pair of snap fits. Utilizing a pre-optimized dynamic response behavior of the robot we plan trajectory and design parameters of the mating parts, which influence the process dynamics and thus the external excitation of the manipulator dynamics. The expected advantage in industrial applications is a relatively easy implementation, because performance can be improved by simply adjusting 'external' parameters as path and geometry. Particularly, no modifications of the control architecture are required. Application of the proposed approach to a snap joint under practical constraints can reduce the cycle time by more than 45%.

Feedback linearization control considers the nonlinear dynamics of a system. It can be used to control a tele robot online, which reduces vibration excitation. The mechanical model of a new industrial robot with highly non-linear kinematics is developed. Feedback linearization control is tested on it by simulation. Results are compared to a conventional linear single-joint controller.

The paper contributes to the problem of robotic manipulation where the interaction between robot and environment is an essential part of the task. In order to deal with impacts, oscillations and constrained motion, a model-based optimization approach is suggested, which relies on a detailed dynamic model of the manipulator incorporating finite gear stiffnesses and damping. These models are used to define an optimization problem, which is then solved using numerical programming methods. The intention of the proposed method is to provide a tool in the planning stage of an assembly task for an efficient manipulator optimization with respect to increased productivity and reliability. It is illustrated with an assembly task, namely inserting a rigid peg into a hole with a PUMA 562 manipulator. The robot's position and its control coefficients, which have a large influence on its dynamic response behavior, are adjusted according to the specific needs of the manipulation task to be carried out. The expected advantage in industrial applications is a comparatively easy implementation, because performance can be improved by simply adjusting "external" parameters such as mating position and coefficients of the standard joint controller. Particularly, no modifications of the control architecture and no additional hardware are required.

A method for the planning of robotic assembly by numerical optimization of position and joint controller coefficients is proposed in this paper. Starting from a detailed modelling of the robot's dynamics incorporating joint elasticities and damping, scalar optimization criteria are formulated, the minimization of which yields an improved performance during assembly. Together with constraints ensuring practical applicability a nonlinear vector optimization problem is stated for a peg-inhole insertion task and solved using an SQP-algorithm. Discussion of the Pareto-optimal region for this example shows that the dynamic performance of the robot can be tuned within a wide range according to the specific properties of the mating process by adjusting the robot's position and its joint controller coefficients. Although finding an absolute minimum of the cost functions requires rather strong restrictions, an automatic optimization routine can be expected to work more effectively than an intera...

Models and model parameters form the base of a computer aided planning of robot manipulations. The identification procedure presented determines the independent, dynamic parameters by trajectories of optimal excitation without the need of disassembling the robot. Joint parameters are identified by fixing the arms and performing static and dynamic tests where the actuators represent an excitation source. A comparison of measurement and calculation verifies the results for a PUMA 562 robot.

In this paper the sensitivity to interference between a robot and its environment is examined. We establish rules for generating robot trajectories which maximize the robots capabilities with respect to exerting forces while minimizing the strain on the drives. Another aspect is the calculation of the maximal tolerable position error that guarantees a certain assembly task to be completed within pre-defined force limits. Applying impact dynamics yields the impact forces when the mating parts come into contact. The transfer behavior of the robot to avoid unwanted oscillations under dynamically varying loads is examined. The dynamical model of the robot includes elasticity, damping, friction and backlash in the joints. The parts to be assembled may be rigid or elastic with Coulomb friction acting between them. The calculation methods are explained in detail and measurements conducted on a PUMA 562 robot complete the approach.

This paper deals with planning assembly processes for a manipulator using numerical simulations, so that the load on the parts and the dynamics of the robot during the part insertion can be studied. Typical for mating processes is the contact of the robot with its environment through the parts. The arising contact forces influence the motion of the robot. For numerical simulations we have to describe this operation with mechanical models. We present the dynamical model of the manipulator and models for mounting processes. Different methods are applied depending on the mechanical properties of the parts. With compliant mating parts, the forces and moments are only dependent on the position and the velocity of the robot's gripper with respect to the environment. If the mating parts are very stiff, the dynamics of the robot is characterized by closed loops, which requires special mathematical treatment. Numerical and experimental results illustrate our approaches.

Deals with planning assembly processes for a manipulator using numerical simulations. The dynamical model of the robot includes elasticity, damping, friction and backlash in the joints. In addition several models of typical mounting processes are used to calculate the forces and torques acting on the gripper during the assembly task. In this paper the authors specifically present the modelling of elastic rings, typically made of rubber, mounted on a piston for the insertion into a hole, whose walls may contain notches. The nonlinear and unsteady forces acting during the mounting process are then evaluated. The influence on the manipulator is regarded via the coupling of the authors' process model with the dynamic robot model. This approach is then verified experimentally.>

The paper presents a survey of the six-legged walking robot designed and constructed at the Institute of Mechanics at the Technical University in Munich. This robot was designed in 1993 with special regard for principles found in natural walking of hexapods, which walk and climb very efficiently over arbitrary irregular surfaces. The investigated insect and its main features are presented. A description of the mechanical hardware and electronics used in the robot is included.>

In the last two years, a dextrous hydraulic hand has been developed at the Lehrstuhl B fur Mechanik. As with all dextrous hands, in order to be able to manipulate objects effectively, the TUM Hand requires not only a sound construction and robust low-level control but also high level grasp planning. This paper discusses some of the high level grasp strategies used with the TUM Hand. The strategies presented have two main functions: the calculation of the grasp points and finger forces, and the positioning of the object within the hand. First, methods for calculating the grasp points and finger forces are presented. A decomposition of the finger forces into their normal and tangential, rather than internal and manipulation components is used. Once the grasp points and the finger forces are known, the problem of correctly placing the object within the hand can be considered. This paper describes the method used to locate and orient the hand relative to the object such that the fingers can reach their corresponding grasp points.>

The authors extend the application of a multilayered feedforward network to the hybrid position/force control problem. Using the measured positions and forces during an assembly task as inputs to a neural network, the necessary selection matrix and artificial constraints can be computed by the network. The authors use the peg-in-the-hole insertion problem to demonstrate their method. The neural network hybrid position/force controller is shown to correctly switch to the required position and force control modes and to recall the desired positions and forces required for each subcontrol task.

The authors present a study of the geometrical aspects, the inverse and direct dynamics and the control design for a six-legged walking machine. They take special regard to the design and control concepts used by nature in six-legged insects, which walk and climb very efficiently over arbitrary irregular surfaces.

During assembly operations the manip- ulator's motion is subject to various constraints that correspond to the current contact configuration. Part mating processes are therefore generally typified by structure-variant dynamic systems which are charac- terized by the fact that their number of degrees of free- dom may vary depending on the system state. Based on the manipulator's open loop dynamics and a La- grangian approach we present a dynamic model for the representation of assembly processes that takes into account both aspects of impact and stick-slip phenom- ena as well as elastic deformations of the mating parts. The evaluation is supported by an algorithm that au- tomatically generates the correct set of equations of motion and the respective constraint forces. Numeri- cal and experimental results illustrate the approach.

A position and force control concept for a manipulator with elasticity in joints and links is developed. The measurement of the link deformations is used for control of vibrations as well as for determining of contact forces. Two cases are distinguished: for fast movements on a contact surface, a multistage approach is applied that consists of an offline feedforward branch and an online elasticity controller; and for slow compliant movements, an impedance control algorithm is used that includes elasticity feedback to damp vibrations of the elastic links. A three-DOF (degree-of-freedom) manipulator with two links that are elastic with respect to bending and torsion is used for verification of the concept in experiments.>

In order to gain insight into the biological constructional conception of walking as a basis for future technical developments, the gait dynamics of the walking stick insect (Carausies morosus) is investigated. It is modeled by a rigid multibody system consisting of 19 bodies and forming multiple closed kinematic chains corresponding to the regarded gait pattern. Thus, the changing structure during the walking motion yields a dynamic system with time-varying topology. The results of the computer simulation are compared with measurements of the insects, confirming the possibility of modeling natural walking motion by mechanical means.>

The control of an elastic robot along a reference trajectory is performed in several steps. An optimal reference path for a rigid robot is generated, taking into account any restrictions and arbitrary robot/trajectory configurations. Tracking of that path is improved by regarding the elastic influences of all links and joints. For the purpose the robot is modeled as an elastic multibody system. A control scheme is added which feeds back strain-gauge measurements at the elastic arms to damp remaining oscillations. These three stages together allow high performance control of an elastic robot, which is proven by measurements at a three-degree-of-freedom laboratory robot.>

A way to find the optimal trajectory of an arbitrary manipulator following a prescribed path is described. The method takes advantage of the fact that in this case overall motion takes place with one degree of freedom (DOF) only. Transforming the equations of motion to this one DOF results in a set of equations which defines the phase space of admissible motion constrained by path geometry and joint torques in a transparent way. The time optimal solution representing the maximum mobility of the path-manipulator configuration can be easily determined by a field of extremals bound by a maximum velocity curve, which acts as a trajectory source or sink. Its properties lead to an algorithm for evaluating the time-minimum curve from a sequence of accelerating/ decelerating extremals. Additional optimizing criteria are studied by applying Bellman's principle.

Following a prescribed trajectory with a manipulator tip in an ideal manner results in a one DOF overall motion whatever the configuration of the manipulator and of the path might be. Thus, a transformation of the equations of motion from joint coordinates to path coordinates leads to a set, which cannot only be solved by formal quadrature but defines as well the phase space of admissible motion constrained by path geometry and joint torques. Time optimal solution representing the maximum mobility of the path-manipulator-configuration can be determined by a field of extremals bounded by a maximum velocity curve, which acts as a trajectory source or sink. Its properties lead to an algorithm for evaluating the time-minimum-curve from a sequence of accelerating/decelerating extremals. Additional optimizing criteria are regarded applying Bellman's principle.