R. Ceres

The MANUS-HAND Dextrous Robotics Upper Limb Prosthesis: Mechanical and Manipulation Aspects

Dextrous artificial hand design and manipulation is an active research topic. A very interesting practical application is the field of upper limb prosthetics. This paper presents the mechanical design and manipulation aspects of the MANUS-HAND project to develop a multifunctional upper limb prosthesis. The kinematics of our design makes use of the so-called underactuated principle and leads to an innovative design that triples the performance of currently existing commercial hand prosthesis. In addition, the thumb design allows its positioning both in flexion and opposition. As a consequence, up to four grasping modes (cylindrical, precision, hook and lateral) are available with just two actuators.The proposed impedance control approach allows the fingers to behave as virtual springs. Given the difficulty of including the user in the control loop, this approach is based on an autonomous coordination and control of the grasp. As a consequence, the requirements on the Human Machine interface are reduced. At the end of the paper, we briefly describe the clinical trials that were set up for evaluation purposes.

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.

A robotic vehicle for disabled children

One of the most frequent effects of physical disability is reduced or impaired mobility. There are a number of technical aids for all the cases of physical impairment but none of the systems described in the literature address the particular problems of children affected by neuromotor disorders accompanied by mental retardation. The following addresses the development of the PALMA [(plataforma de apoyo ludico a la movilidad alternative) (assistive platform for alternative mobility)] system as a tool to assist the mobility of children affected by cerebral palsy. PALMA is specifically adapted to a personalized and early cognitive development of children affected by severe neuromotor problems. The rehabilitation process based on PALMA has an impact on the interaction between children and environment, on their motor dexterity, and on decision-making ability.

Empowering and assisting natural human mobility: The simbiosis walker

This paper presents the complete development of the Simbiosis Smart Walker. The device is equipped with a set of sensor subsystems to acquire user-machine interaction forces and the temporal evolution of users feet during gait. The authors present an adaptive filtering technique used for the identification and separation of different components found on the human-machine interaction forces. This technique allowed isolating the components related with the navigational commands and developing a Fuzzy logic controller to guide the device. The Smart Walker was clinically validated at the Spinal Cord Injury Hospital of Toledo - Spain, presenting great acceptability by spinal chord injury patients and clinical staff.

Measuring the 3D-position of a walking vehicle using ultrasonic and electromagnetic waves

The knowledge of the true position of a walking machine (rover) in an inertial reference frame is a problem of paramount importance for realistic application of mobile robots. The points of the robot follow three-dimensional trajectories even on even terrain. When no position feedback is possible, a good knowledge of the dynamical behaviour of the rover is needed to get an estimation of the position and orientation of the robot. There already exist some sophisticated optical systems which track the path followed by specific (lighted) points of the robot. Although these systems can provide very precise measurements, they cannot cover larger areas with the same precision. This paper presents a laboratory prototype capable of measuring the position of a four-legged walking robot using a combination of electromagnetic (EM) and ultrasonic (US) waves produced by a spark-generator, avoiding any physical link between the robot and the environment.The 3D position is obtained from range data that can be estimated from the travel time of the acoustical wave from the sparking point to three static receivers. The EM wave is used for synchronization. The system provides real time data to operate in a wider space than the optical systems. After the processing and filtering of the signal, a final precision better than 1 mm is reached in a work range of about 5 m. The track-data obtained by the position meter is used to know the dynamic behaviour of the robot and to study the improvement introduced by the use of inclinometers.

Ultrasonic sensor for liquid-level inspection in bottles

Abstract In this paper, the development of a precise and dynamic ultrasonic distance sensor to measure the level of liquid in bottles for an industrial line is described. For this application, optical, capacitive or mechanical means are not suitable. In the first part the limitations of a conventional pulse-echo ranging system are discussed. A strategy to measure the time of flight based on the envelope of the echo signal is performed, solving in a practical way the problem of the complex signal reflected from the main surface, meniscus and internal walls of the bottleneck.

Novel modeling technique for the stator of traveling wave ultrasonic motors

Traveling wave ultrasonic motors (TWUM) are a promising type of piezoelectric transducers, which are based on the friction transmission of mechanical propagating waves. These waves are excited on the stator by using high Q piezoelectric ceramics. This article presents a modeling strategy, which allows for a quick and precise modal and forced analysis of the stator of TWUM. First-order shear deformation laminated plate theory is applied to annular subdomains (super-elements) of the stator. In addition to shear deformations, the model takes into account the effect of rotary inertia, the stiffness contribution of the teeth, and the linear varying thickness of the stator. Moreover, the formulation considers a more realistic function for the electric field inside the piezoelectric ceramic, i.e., a linear function, instead of the generally assumed constant electric field. The Ritz method is used to find an approximated solution for the dynamic equations. Finally, the modal response is obtained and compared against the results from classical simplified models and the finite element method. Thus, the high accuracy and short computation times of the novel strategy were demonstrated.