Towards a neural hierarchy of time scales for motor control

Animals show remarkable rich motion skills which are still far from realizable with robots. Inspired by the neural circuits which generate rhythmic motion patterns in the spinal cord of all vertebrates, one main research direction points towards the use of central pattern generators in robots. On of the key advantages of this, is that the dimensionality of the control problem is reduced. In this work we investigate this further by introducing a multi-timescale control hierarchy with at its core a hierarchy of recurrent neural networks. By means of some robot experiments, we demonstrate that this hierarchy can embed any rhythmic motor signal by imitation learning. Furthermore, the proposed hierarchy allows the tracking of several high level motion properties (e.g.: amplitude and offset), which are usually observed at a slower rate than the generated motion. Although these experiments are preliminary, the results are promising and have the potential to open the door for rich motor skills and advanced control

Design and Tests on the 30 to 600 A HTS Current Leads for the Large Hadron Collider

Some 800 correction magnets of the Large Hadron Collider will be individually powered. Each of them needs a pair of current leads. To reduce the heat leak through these leads, the current has been chosen as low as reasonably possible, 30 to 600 A. For the same reason CERN started in-house a development of current leads using commercial bulk BSCCO-2212 material.This paper discusses the design and the test results of this lead. We tested several prototypes, measured the heat leak through the lead, studied and tested what happens if the lead is brought to critical temperature causing it to quench

Superconducting Sextupole Corrector Magnet for the LHC Main Dipoles

Each LHC main dipole will be equipped with small sextupole corrector ma g nets with a field strength of 1970 x2 T/m2 and a magnetic length of 100 mm designed to correct the sextupole field errors. The paper presents a cosine-q type of design where much emphasis has been put on the cost reduction because these magnets have to be made in large series of some 2500 pieces. We describe the design of a two-layer coil which can be wound automatically. The winding starts in the middle of the wire with the only joggle, the layer jump, which is housed in a corresponding groove in the end of the central island. The two layers are wound simultaneously turning in opposite directions to find their position without the need of local tooling. The coil ends are closely packed and need no end spacers. The 18 pole perturbation introduced by the ends is corrected by the position of the coil block in the straight part. The yoke is made of iron laminations of the "Scissors type" which transmit the pre-stress from the outer aluminium shrink ring to the coil. This allows the iron to be close to the coil for field enhancement and also boosts the pre-stress in the coil due to the cool down contractions. The paper describes the experience with the magnet construction and gives the first test results

Simulation of the Effect of a Series of Superconducting Magnets on a Quenching Magnet using a Controlled Current Pulse

In the LHC, the superconducting corrector magnets will be powered in series of up to 154 magnets. For protection in case of a quench, each magnet has been equipped with a parallel resistor as a bypass for the current. To validate and optimize the parallel resistor value, a test arrangement has been set up which allows quenching a single magnet as if it were connected in a large series of magnets. This simulation is obtained by maintaining the current for a certain time interval after the quench occurred. Calculations have shown that, depending on the magnet type, a current duration (after quench) of 0.2 s to 1 s simulates correctly the effect of the series of magnets. The paper gives calculation results comparing the real situation with the simulated one and reports on the test set-up that will be used to optimize the parallel resistors

Learning and Composing Primitive Skills for Dual-Arm Manipulation

In an attempt to confer robots with complex manipulation capabilities, dual-arm anthropomorphic systems have become an important research topic in the robotics community. Most approaches in the literature rely upon a great understanding of the dynamics underlying the system's behaviour and yet offer limited autonomous generalisation capabilities. To address these limitations, this work proposes a modelisation for dual-arm manipulators based on dynamic movement primitives laying in two orthogonal spaces. The modularity and learning capabilities of this model are leveraged to formulate a novel end-to-end learning-based framework which (i) learns a library of primitive skills from human demonstrations, and (ii) composes such knowledge simultaneously and sequentially to confront novel scenarios. The feasibility of the proposal is evaluated by teaching the iCub humanoid the basic skills to succeed on simulated dual-arm pick-and-place tasks. The results suggest the learning and generalisation capabilities of the proposed framework extend to autonomously conduct undemonstrated dual-arm manipulation tasks.Comment: Annual Conference Towards Autonomous Robotic Systems (TAROS19