Viviane Pasqui

How can human motion prediction increase transparency

A major issue in the field of human-robot interaction for assistance to manipulation is transparency. This basic feature qualifies the capacity for a robot to follow human movements without any human-perceptible resistive forces. In this paper we address the issue of human motion prediction in order to increase the transparency of a robotic manipulator. Our aim is not to predict the motion itself, but to study how this prediction can be used to improve the robot transparency. For this purpose, we have designed a setup for performing basic planar manipulation tasks involving movements that are demanded to the subject and thus easily predictable. Moreover, we have developed a general controller which takes a predicted trajectory (recorded from offline free motion experiments) as an input and feeds the robot motors with a weighted sum of three controllers: torque feedforward, variable stiffness control and force feedback control. Subjects were then asked to perform the same task but with or without the robot assistance (which was not visible to the subject), and with several sets of gains for the controller tuning. First results seems to indicate that when a predictive controller with open loop torque feedforward is used, in conjunction with force- feedback control, the interaction forces are minimized. Therefore, the transparency is increased.

Design and acceptability assessment of a new reversible orthosis

We present a new device aimed at being used for upper limb rehabilitation. Our main focus was to design a robot capable of working in both the passive mode (i.e. the robot shall be strong enough to generate human-like movements while guiding the weak arm of a patient) and the active mode (i.e. the robot shall be able of following the arm without disturbing human natural motion). This greatly challenges the design, since the system shall be reversible and lightweight while providing human compatible strength, workspace and speed. The solution takes the form of an orthotic structure, which allows control of human arm redundancy contrarily to clinically available upper limb rehabilitation robots. It is equipped with an innovative transmission technology, which provides both high gear ratio and fine reversibility. In order to evaluate the device and its therapeutic efficacy, we compared several series of pointing movements in healthy subjects wearing and not wearing the orthotic device. In this way, we could assess any disturbing effect on normal movements. Results show that the main movement characteristics (direction, duration, bell shape profile) are preserved.

Wireless Wearable T-Shirt for Posture Monitoring During Rehabilitation Exercises

The monitoring of any human physiological parameters during rehabilitation exercises requires noninvasive sensors for the patient. This paper describes a wireless wearable T-shirt for posture monitoring during rehabilitation or reinforcement exercises. The subject posture is measured through a sensorized T-shirt using an inductive sensor sewn directly on the fabric. The wireless wearable T-shirt design specifications are the following: independence from the remote unit, easy to use, lightweight and comfort of wearing. This paper reports the conceptual framework, the fabricated device description, and the adopted experimental setup. The instrumented T-shirts output data are compared with the data obtained via an optical system, as a gold standard, that measures the marker positions over the patients back and chest. The trials performed on four subjects obtained on different days demonstrate that the wireless wearable sensor described in this paper is capable of producing reliable data compared with the data obtained with the optical system. The constitutive sensor simplicity that includes only a copper wire and a separable circuit board allows achieving the objectives of simplicity, ease of use, and noninvasiveness. The sensorized T-shirt, integrated with designed conditioning and transmission electronics for remote communication, could be used as a support tool for postural monitoring during rehabilitation exercises.

A geometrical approach to the trajectory planning of a snake-like mechanism

The hyper-redundancy concept and related mechanisms are of special interest in robotics research. Trajectory planning and obstacle avoidance seem to be the main research areas where the use of hyper-redundancy is considered. However, there are few prototypes of this kind of robots. The present work is the introductory part of a larger study aiming at the construction of a hyper-redundant, snake-like robot supposed to progress as a real snake, without limbs or wheels. It represents a first approach to a simulation of a snake-like mechanism in order to get basic characteristics of a such locomotion.

A Reactive Robotized Interface for Lower Limb Rehabilitation: Clinical Results

This paper presents clinical results from the use of monitor-nomad (MONIMAD), which is a reactive robotized interface for lower limb rehabilitation of patients suffering from cerebellar disease. The first problem to be addressed is the postural analysis of sit-to-stand motion. Experiments with healthy subjects were performed for this purpose. Analysis of external forces shows that sit-to-stand transfer can be subdivided into several phases: preacceleration, acceleration, start rising, and rising. Observation of center of pressure, ground forces, and horizontal components force on handles yields rules that identify the stability of the patient and adjust the robotic interface motion to the human voluntary movement. These rules are used in a fuzzy-based controller implementation. The controller is validated on experiments with diseased patients at Bellan Hospital, Paris, France.

Sit to Stand Transfer Assisting by an Intelligent Walking-Aid

The sit to transfer assisting for elderly patients using an intelligent walking-aid is presented. This assistive device provides physical support to aid elderly with physical impairment during both the walk and the sit-to-stand transfer. In this paper, we will focus on the sit-to-stand transfer function and more precisely on the trajectory generation of the assistive device handles using interpolating cubic splines.

A new description of scapulothoracic motion during arm movements in healthy subjects

The participation of scapula motion in arm movement is clinically well known and recent three dimensional (3D) analyses using kinematic techniques have confirmed its importance. Scapular motion relative to the thorax has a theoretical maximum of 6 degrees of freedom (DoF), resulting from rotations at both clavicular joints (3 rotational DoF each). However, most recent kinematic studies have only analysed the 3D rotations of the scapula relative to the thorax. In the present study, the 3D translations of the barycentre of the scapula were considered in order to complete the description of movement at the shoulder complex. Eight healthy subjects performed arm elevation in the sagittal and frontal planes, simulated activities of daily living (hair combing and back washing) and maximum voluntary scapula movement (forward and backward rolling). Measurements were recorded using a 6 DoF electromagnetic device and the acromial method of analysis was used. The results showed that 3D scapular rotations and translation of its barycentre were functionally consistent for all tasks. A principal component analysis (PCA) yielded three factors, explaining 97.6% of the variance. The first two factors (protraction and shrug, according to clinical descriptions) combined rotations and translations, consistent with the hypothesis that the scapula rolls over the curved thoracic surface. The third factor related to lateral-medial rotation, thus representing rotation in the plane tangential to the thorax. The PCA suggested that scapular motion can be described using these 3 DoF. This should be studied in a larger group of individuals, including patients with pathological conditions.

Elderly People Sit to Stand Transfer Experimental Analysis

This paper describe an assistive device for the elderly providing support during the sit to stand transfer. A postural stabilization criteria and an assisting force in case of instability are presented.

Characterization of a Least Effort User-Centered Trajectory for Sit-to-Stand Assistance

Sit-to-stand transfer is a prerequisite for locomotion and induces a lot of effort from elderly or disabled people. In the context of a project based on a locomotion and sit-to-stand assistance robotics device, we present a methodology to tune the trajectory of active handles so that the verticalisation effort of the user is minimised. The methodology is user-centered in the sense that the robot will generate a specific trajectory for each particular user.

Fast embedded feet pose estimation based on a depth camera for smart walker

Assisted gait monitoring could benefit from the measurement of feet position and orientation. These measurements could also be used to implement intention-based control laws for smart walkers. Several works have been dedicated to the detection of lower limbs. The proposed methods are usually fast, but only detect the position of the legs. Others may even be more complete, but are not adapted to reactive applications. Also, they often use markers attached on the feet, which is unsuitable in daily routine. In this paper, a fast feet position and orientation detection algorithm is proposed. It is based on a camera depth sensor and does not require the use of any marker. The obtained results are compared with a ground truth provided by a motion traking system to experimentally assess the performances of the proposed algorithm.