D2.1 Requirements and Specification - CORBYS

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D2.1 Requirements and Specification Figure 39: SCHUNK modular smart actuator system with rotary and linear drives as well as gripper modules 14.4 CORBYS enabling potential and constraints (current gaps/shortcomings) With regards to the CORBYS project there are a few criteria to discuss on the dimensions of the motors and control subsystem. Miniaturisation is a major issue because many drives must be incorporated into a relatively small demonstrator (gait rehabilitation). In order to move human joints in an exoskeleton high torque motors with minimised dimensions are needed. An actuator providing a high torque – at low weight is the resulting requirement for the highest power density. Another aspect for dimensioning the drive is heat. The drives will need to be placed near the human skin and must therefore be limited in heat emission. Both demonstrators are mobile systems powered by batteries. This leads to several requirements with regards to power stability and tolerance for a wide voltage range (typically 19... 30VDC). The safety and reliability is a clear issue, because the user must expect highest robustness during their training sessions. The drives must provide a high short time overload capacity, because smaller motors with small power consumption and small size would assist in the dimensioning of the actuators. Minimising friction in motor and gear heads is another important issue helping to significantly improve the sensibility of the drive. The cycle time aspect is based on the controls system coordinating the actuator motion independent of the training program and the sensor feedback system. Ideally, an open control architecture is foreseen allowing the control system to access the drive data and parameters at all times and on different levels. Finally minimal noise is desired in order to enable better acceptance by the human user. Price issues need to be discussed from a dissemination point of view. 14.5 Technology innovation requirements Gaps filter elements Analysing the state of the art in actuator technology revealed several gaps. The first to name is integration of actuators with requirements as described above in a dimension limited mobile device with battery power. In order to keep battery lifetime high the complete system must be optimised for power consumption and high efficiency drive. The high power density of the system leads to possible sensitivity in data transfer, bus communication or malfunction due to power loss. The actuators need to provide variable stiffness, depending on the current control and training scheme. At the same time safety is important to reduce the risk of injuries. For easy service a modular approach and a simplified interfacing with electrical connectors is preferred. 146
D2.1 Requirements and Specification 15 StateoftheArt in NonInvasive Brain Computer Interface (BBT) The objective of CORBYS project is to develop the underlying design principles of a cognitive robotic system with the focus on augmenting human locomotion capabilities. One of the key points of these principles is the way that the human and the robot interact and share their cognitive capabilities. In this area, the large majority of research was concentrated in a uni-directional way, where the human delivers orders to the machine responsible for the execution of the commands. The focus has been on exploring and improving the way that robots understand natural human expressions (e.g. understanding natural language, gestures, etc). However, very little research has concentrated on a mutual exchange of cognitive information. This is because this information mainly resides in the human brain and progress was still required in brain computer interfacing. A few years ago there was much research in understanding how to decode this information from brain imaging techniques, leading to one of the objectives of CORBYS: to use brain computer interface technology to online decode human cognitive information. This information will be used to build a natural way of communication between the human and the robot, and to guide the design and operation principles of the cognitive robot. In this context the Brain-computer interfaces (BCI) emerge as systems that make it possible to translate the electrical activity of the brain in real-time using commands to control devices. They do not rely on muscular activity and can therefore provide communication and control for people with devastating neuromuscular disorders such as the amyotrophic lateral sclerosis, brainstem stroke, cerebral palsy and spinal cord injury. It has been shown that these patients are able to achieve EEG controlled cursor, limb movement, and prosthesis control and have even successfully communicated by means of a BCI (Birbaumer et al, 1999; Hochberg et al, 2006; Buch et al, 2008). The remainder of this Deliverable reviews current non-invasive BCI technology applied to the control of robots focussing on the CORBYS technology gaps and innovations. Subsequently, the main components of a BCI system, Hardware, Software, Basic Signal Processing and Decoding will be described in the following sections, showing the state of the art, the constraints and the respective technology innovations. 15.1 Invasive vs. NonInvasive BCI Technology and Robotics Recently there has been a great surge in research and development of brain-controlled devices for rehabilitation. The most significant characteristic of these systems is the use of invasive or non-invasive methods to record brain activity. Invasive techniques require a clinic intervention to implant the electrodes on the cortex, while non-invasive methods place the sensors outside the skull (e.g., Electroencephalogram EEG). The research arena is dominated by the US for invasive techniques and research in animals, while the EU leads in the development of non-invasive techniques with direct application on humans. On the one hand, US teams have achieved significant results using invasive recording methods to control artificial devices. A rat, for example, was able to move a robotic arm in one dimension to get water (Chapin et al, 1994), monkeys were trained to move a cursor on a screen and adjust its size (Carmena et al, 2003) and to self-feed using a robotic arm with a gripper, to grab food in three dimensions (Velliste et al, 2008), and a patient had sensors implanted directly in the cortex and learned to open and close a prosthetic hand and control a simple robotic arm in two dimensions (Hochberg et al, 2006). These achievements show that direct and online control of a robotic device is possible with invasive brain recordings. However, these settings involve technical and clinical difficulties for humans, such as the maintenance of the electrodes in the cortex, infection risks, and damage to the brain (Mc Farland & J.R.Wolpaw, 2008). On the other hand, in line with CORBYS, much research in BCI has focused on non-invasive recording 147
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CORBYS Cognitive Control Framework
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D2.1 Requirements and Specification
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D2.1 Requirements and Specification - CORBYS

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