Roger Pissard-Gibollet

Detection of Freezing of Gait in Parkinson Disease: Preliminary Results

Freezing of gait (FOG) is a common symptom in Parkinsonism, which affects the gait pattern and is associated to a fall risk. Automatized FOG episode detection would allow systematic assessment of patient state and objective evaluation of the clinical effects of treatments. Techniques have been proposed in the literature to identify FOG episodes based on the frequency properties of inertial sensor signals. Our objective here is to adapt and extend these FOG detectors in order to include other associated gait pattern changes, like festination. The proposed approach is based on a single wireless inertial sensor placed on the patients lower limbs. The preliminary experimental results show that existing frequency-based freezing detectors are not sufficient to detect all FOG and festination episodes and that the observation of some gait parameters such as stride length and cadence are valuable inputs to anticipate the occurrence of upcoming FOG events.

Development of a Reactive Mobile Robot Using Real Time Vision

In this paper, we discuss both theoretical and implementation issues of a vision based control approach applied to a mobile robot. After having briefly presented a visual servoing framework based on the task function approach, we point out some problems of its application to the case of mobile nonholonomic robots. We will show how by using additional degrees of freedom provided by an manipulator arm, we can overpass these difficulties by introducing redundancy with respect to the task. The second part of the paper deals with the development of an experimental testbed specially designed to rapidly implement and validate reactive vision based tasks. It is constituted by a mobile robot carrying an hand-eye system using a dedicated vision hardware based on VLSIs and DSP 96002s processors which allows to perform image processing at video rate. Programming aspects are fully taken into account from tasks level specification up to real time implementation by means of powerfull software tools handling explicitely reactivity and real time control issues.

Reactive Mobile Robots Based on a Visual Servoing Approach

This paper deals with vision based control applied to autonomous mobile robots. The general a proach in robot vision separates vision from control htat ic look and move). A n alternative way consists to specify the problem tn terms of control directly into the sensor frame. This approach seems t o be Q fruitful way for implementing robotics tasks based on reactivity concept. We introduce a low level task specification b y the notion of virtual linkage. This virtual linkage can be expressed b y a set of constraints on the motion of a frame linked to 2he robot with respecf t o a certain frame associated to the environnment. It seems interesting to apply such a vision based control to a mobile robot. The robot considered here is a two wheels driven nonholonomic car? with a camera mounted on 3 d.0.f manipulator. In this siudy we consider the whole mechanical system constituted by the cart and i f s manipulator like a single kinematic chain. So in adding the degrees of freedoom of the a m i o the cart, it becomes possible to fully control the trajectory of the effector. In order to validate this approach, a simulation loo1 has been developped in Mathematica. A first application concerns automatic exploration and cartography of an unknowm room by wall following techniques.

Can an Underactuated Leg with a Passive Spring at the Knee Achieve a Ballistic Step

In this paper, we present a control scheme aimed at moving an underactuated double pendulum simulating a leg. The system is actuated at the hip and includes a spring at the knee. It interacts with the ground, which is in fact a treadmill, through a telescopic foot made of a linear spring and a damper. The control scheme is different in the 2 phases, swing and stance, and a repetitive step is achieved by switching between these two controls. The paper describes the system, the used models and the control algorithms. It presents also experimental results of the approach.