Joachim Denk

Experiments in vision-guided biped walking

Goal-oriented vision-guided biped locomotion requires a high degree of coordination between perception and walking. How to establish this coordination remains a fundamental and rarely studied problem in legged robotics. Some of our investigations into this field are outlined in this article by presenting recent results in vision-guided biped locomotion. The guidance and control approaches developed are experimentally validated on the biped robot BARt-UH. It is shown how perception techniques are employed in closed-loop for step sequence adaptation and locomotion control of a walking machine.

Synthesis of walking primitive databases for biped robots in 3D-environments

This paper presents a systematic approach to generate walking primitive databases for anthropomorphic 3D-bipeds allowing step length adaptation, direction changes and stepping over obstacles. The individual walking primitives are derived by optimal control techniques. Zero moment point (ZMP) and friction conditions at the feet ensuring postural stability of the biped, as well as bounds on the joint angles and on the control torques, are treated as constraints. The resulting reference trajectories are validated by dynamic simulations.

Active magnetic bearing systems with standard drive technology for large turbo machines

In the Oil & Gas industry, the primary bearing is an oil sleeve bearing. Around two decades ago, active magnetic bearings (AMB) were introduced into the market but they never gained a relevant market share in large turbo machinery. This paper discusses how standard drive technology can be successfully adapted to control AMB systems. Furthermore, results of prototype testing with large turbo machinery and the advantages regarding commissioning and service are presented. The benefits of using standard drive technology for commissioning and service are discussed and results of a prototype test are presented.

Industrialization of AMB Systems With Standard Drive Technology

Around two decades ago, active magnetic bearings (AMBs) were introduced into oil and gas applications but never gained any relevant market share in large turbomachinery drive trains. This paper discusses how standard drive technology from machine tool applications can be used to control AMB systems. As a proof of the concept, results of prototype testing with a 5-MW induction motor are presented.

Practical Experience with Vision-guided Biped Walking

This paper presents key ideas of our approach to perception-based biped robot walking. Computer vision techniques are employed for reactive adaptation of the stepsequence taking into account the restrictions imposed by dynamics and mechanical construction of the walking machine. The vision-based approach and guidance system were evaluated by experiments with the biped robot BARt-UH.

Mechatronic design of direct drive systems

In contrast to conventional drives, with direct drives the motor is not created until it is integrated into the machine. The mechanical and electrical subsystems are merged to form the mechatronic system by the velocity and position control loops. Since control parameters have a crucial influence on the behavior of the complete system, a main goal of this article is to explain their importance for machine characteristics such as stiffness and dynamics. The disturbance behavior of directly driven systems is discussed in detail. Using the balance theorem, it is shown why an increase in stiffness gained by control in one frequency spectrum is always interconnected with a loss of stiffness for other frequencies. A finite element model of a roll serves to explain the modeling approach for directly driven machines and to show how the system stiffness can be increased by a proper choice of the encoder position

Aktive Magnetlagerung für Turbomaschinen auf Basis von Standardantriebstechnik

Zusammenfassung Dieser Artikel beschreibt, wie zuverlässige Standardantriebsregelungstechnik und Standardleistungsteile, die in Werkzeugmaschinenanwendungen in hoher Stückzahl zum Einsatz kommen, genutzt werden können, um Magnetlager in Turbomaschinenanwendungen anzusteuern. Als Nachweis für die Tragfähigkeit des Ansatzes werden Ergebnisse von Prototypentests mit einem 5-MW-Asynchronmotor sowie eine Kundenprototypenanwendung mit einem 23-MW-Kompressorstrang präsentiert.