Florian Petit

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Whereas short-term memory lasts from minutes to hours, long-term memory (LTM) can last for days or even an entire lifetime. LTM generally forms after spaced repeated training sessions and involves the regulation of gene expression, thereby implicating transcription factors in the initial steps of LTM establishment. However, the direct participation of(More)
Variable Impedance Actuators (VIA) have received increasing attention in recent years as many novel applications involving interactions with an unknown and dynamic environment including humans require actuators with dynamics that are not well-achieved by classical stiff actuators. This paper presents an overview of the different VIAs developed and proposes(More)
In this dissertation we study how motion induced through the interaction of inertia, gravity, and elastic oscillations can be utilized to improve the performance of legged robots. Different ‘gaits’ for which such natural dynamics help to optimize efficiency and locomotion speed are synthesized and analyzed for two types of conceptual models: for(More)
Anthropomorphic robots that aim to approach human performance agility and efficiency are typically highly redundant not only in their kinematics but also in actuation. Variable-impedance actuators, used to drive many of these devices, are capable of modulating torque and impedance (stiffness and/or damping) simultaneously, continuously, and independently.(More)
An anthropomorphic hand arm system using variable stiffness actuation has been developed at DLR. It is aimed to reach its human archetype regarding size, weight and performance. The main focus of our development is put on robustness, dynamic performance and dexterity. Therefore, a paradigm change from impedance controlled, but mechanically stiff joints to(More)
Robots with joint elasticity find increasing interest in many research areas. A common design goal is to achieve as little mechanical joint damping as possible. To still achieve system damping often control systems are used. Here, we present a model-free approach to achieve damping via exploiting the kinetic to potential energy transformation process of the(More)
The concept of variable stiffness actuation (VSA) for robotic joints promises advantages regarding robustness, energy efficiency, and task adaptability. The VS joints developed at DLR show very low intrinsic damping for efficient energy storage and retrieval whereas the desired damping behavior for task execution needs to be implemented in control. Robotic(More)
The paper presents a new energy shaping control design for a class of underactuated Euler-Lagrange systems. Flexible joint robots, Series Elastic Actuators, and Variable Impedance Actuated Robots Albu-Schäffer et al. [2008] belong for example to this class. First, classical PD control with feed-forward compensation is revisited and a novel, straight-forward(More)
Strict requirements must be met before robotic systems can be implemented in a human environment, for example, as service robots. Robustness, task adaptability, and energy efficiency are key aspects in this regard. Variable stiffness robots have been shown to be one step toward achieving these standards. In this article, we elaborate on the essential(More)
A new ornithine carbamoyltransferase variant is described with a nearly normal specific enzymatic activity. This new variant is characterized by a ten-fold increased Km value for L-ornithine (3.75 vs. 0.33 mmol/l in control) and by a normal Km value for carbamoylphosphate (0.42 vs. 0.29 mmol/l). Its pH optimum is shifted towards the alkaline side. This(More)