J.L. Pons

Design and Validation of a Rehabilitation Robotic Exoskeleton for Tremor Assessment and Suppression

Exoskeletons are mechatronic systems worn by a person in such a way that the physical interface permits a direct transfer of mechanical power and exchange of information. Upper limb robotic exoskeletons may be helpful for people with disabilities and/or limb weakness or injury. Tremor is the most common movement disorder in neurological practice. In addition to medication, rehabilitation programs, and deep brain stimulation, biomechanical loading has appeared as a potential tremor suppression alternative. This paper introduces the robotic exoskeleton called WOTAS (wearable orthosis for tremor assessment and suppression) that provides a means of testing and validating nongrounded control strategies for orthotic tremor suppression. This paper describes in detail the general concept for WOTAS, outlining the special features of the design and selection of system components. Two control strategies developed for tremor suppression with exoskeletons are described. These two strategies are based on biomechanical loading and notch Altering the tremor through the application of internal forces. Results from experiments using these two strategies on patients with tremor are summarized. Finally, results from clinical trials are presented, which indicate the feasibility of ambulatory mechanical

Automatic fruit recognition: A survey and new results using Range/Attenuation images

An automatic fruit recognition system and a review of previous fruit detection work are reported. The methodology presented is able to recognize spherical fruits in natural conditions facing difficult situations: shadows, bright areas, occlusions and overlapping fruits. The sensor used is a laser range-finder giving range/attenuation data of the sensed surface. The recognition system uses a laser range-finder model and a dual color/shape analysis algorithm to locate the fruit. The three-dimensional position of the fruit, radius and the reflectance are obtained after the recognition stages. Results for a set of artificial orange tree images and real-time considerations are presented.

A vision system based on a laser range-finder applied to robotic fruit harvesting

Abstract. This paper describes a laser-based computer vision system used for automatic fruit recognition. It is based on an infrared laser range-finder sensor that provides range and reflectance images and is designed to detect spherical objects in non-structured environments. Image analysis algorithms integrate both range and reflectance information to generate four characteristic primitives which give evidence of the existence of spherical objects. The output of this vision system includes 3D position, radius and surface reflectivity of each spherical object. It has been applied to the AGRIBOT orange harvesting robot, where it has obtained good fruit detection rates and unlikely false detections.

Design and implementation of an aided fruit‐harvesting robot (Agribot)

This work presents a robot prototype designed and built for a new aided fruit‐harvesting strategy in highly unstructured environments, involving human‐machine task distribution. The operator drives the robotic harvester and performs the detection of fruits by means of a laser range‐finder, the computer performs the precise location of the fruits, computes adequate picking sequences and controls the motion of all the mechanical components (picking arm and gripper‐cutter). Throughout this work, the specific design of every module of the robotized fruit harvester is presented. The harvester has been built and laboratory tests with artificial trees were conducted to check range‐finder’s localization accuracy and dependence on external conditions, harvesting arm’s velocity, positioning accuracy and repeatability; and gripper‐cutter performance. Results show excellent range‐finder and harvesting arm operation, while a bottleneck is detected in gripper‐cutter performance. Some figures showing overall performance are given.

Estimating the 3D-position from time delay data of US- waves: Experimental analysis and a new processing algorithm.

This paper presents an analysis of the main sources of error in a 3D-positioning system using ultrasonic waves, coming to different technical improvements. We suggest a new processing algorithm that will overcome the main sources of error encountered in practice. Comparing with existing processing methods, the proposed technique shows an error reduction by a factor of 20, making the system especially robust against outliers measurements.

Multimodal BCI-mediated FES suppression of pathological tremor

Tremor constitutes the most common movement disorder; in fact 14.5% of population between 50 to 89 years old suffers from it. Moreover, 65% of patients with upper limb tremor report disability when performing their activities of daily living (ADL). Unfortunately, 25% of patients do not respond to drugs or neurosurgery. In this regard, TREMOR project proposes functional compensation of upper limb tremors with a soft wearable robot that applies biomechanical loads through functional electrical stimulation (FES) of muscles. This wearable robot is driven by a Brain Neural Computer Interface (BNCI). This paper presents a multimodal BCI to assess generation, transmission and execution of both volitional and tremorous movements based on electroencephalography (EEG), electromyography (EMG) and inertial sensors (IMUs). These signals are combined to obtain: 1) the intention to perform a voluntary movement from cortical activity (EEG), 2) tremor onset, and an estimation of tremor frequency from muscle activation (EMG), and 3) instantaneous tremor amplitude and frequency from kinematic measurements (IMUs). Integration of this information will provide control signals to drive the FES-based wearable robot.

Nonlinear Performance Index (npi): A Tool for Manipulator Dynamics Improvement

The precise control of manipulators depends nonlinearly on the velocity of the motion as well as on manipulator configuration and commanded acceleration requiring complex control strategies. This paper presents a useful tool for identifying and quantifying nonlinear effects appearing during the motion of any manipulator, the Nonlinear Performance Index (npi). The npi takes into account not only the geometrical parameters defining the manipulator but also its structural dynamics through the use of inertial parameters like mass, inertia, centre of mass... The npi can be used in the design stage for analysing and reducing these undesirable nonlinear effects in any general motion or in the trajectory planning looking for paths along which more precise control is expected. The last part of the paper shows how this design optimisation and path planning has been applied to the Agribot, a fruit picking robot designed at the IAI.

A new platform based on IEEE802.15.4 wireless inertial sensors for motion caption and assessment

Systems for motion caption and assessment in biomechanics are mostly based on photogrammetry. These systems are restricted to the movement analysis lab and moreover, they are very expensive. New advances in MEMs (Microelectromechanical) and wireless technologies enable inertial sensing as an alternatives for motion caption. This paper presents a wireless inertial sensor including 3 linear accelerometers, 3 gyroscopes and 3 magnetometers. The IMU (inertial measurement unit) includes a IEEE802.15.4 compliant transceiver. The platform expands the frontiers of movement analysis for motion caption in real scenarios like sports and wearable robotics since it does not need structurated labs. Besides the advantages, the cost of the platform is much lower comparing actual photogrammetry systems.

Rationale for Multiple Compensation of Muscle Weakness Walking with a Wearable Robotic Orthosis

Exoskeletal devices can provide assistance and supplement to the biological musculoskeletal members. We present a wearable robotic exoskeleton conceived as an improved lower leg orthosis for compensation of human knee and ankle joints disorders provoked by muscle weaknesses during walking, introducing novel biomechanical and user acceptance aspects and daily performance monitoring functionalities.

Application of inertial sensors in rehabilitation robotics

Microelectromechanical systems (MEMS) are revolutionizing a multitude of industries world wide, from consumer products to the scientific community. Rehabilitation robotics is a robotic field specially interested in using the advantages of inertial sensors. The essential aspect in this area is the intrinsic interaction between human and robot, which imposes several restrictions in the design of this sort of robots. This paper addresses the analysis of the application of inertial sensors as sensing technologies in controlled orthotic devices with a detailed analysis with two biomechatronic robotics rehabilitation exoskeletons, one for the upper and other for the lower limb. Eventually, the results and conclusion of the experiments are given.