Antonio Cardenas

Workspace and Payload-Capacity of a New Reconfigurable Delta Parallel Robot

In this paper the workspace and payload capacity of a new design of reconfigurable Delta-type parallel robot is analysed. The reconfiguration is achieved by adjusting the length of the kinematic chains of a given robot link simultaneously and symmetrically during the operation of the robot. This would produce a dynamic workspace in shape and volume. A numerical analysis of the variation of shape and volume of the workspace and payload capacity of the robot is presented. Based both on the results of this analysis and on practical requirements, a proposal for the design of a reconfiguring mechanism is presented.

Robot Positioning Using Camera-Space Manipulation With a Linear Camera Model

This paper presents a new version of the camera-space-manipulation method (CSM). The set of nonlinear view parameters of the classic CSM is replaced with a linear model. Simulations and experiments show a similar precision error for the two methods. However, the new approach is simpler to implement and is faster.

Camera Space Particle Filter for the Robust and Precise Indoor Localization of a Wheelchair

This paper presents the theoretical development and experimental implementation of a sensing technique for the robust and precise localization of a robotic wheelchair. Estimates of the vehicle’s position and orientation are obtained, based on camera observations of visual markers located at discrete positions within the environment. A novel implementation of a particle filter on camera sensor space (Camera-Space Particle Filter) is used to combine visual observations with sensed wheel rotations mapped onto a camera space through an observation function. The camera space particle filter fuses the odometry and vision sensors information within camera space, resulting in a precise update of the wheelchair’s pose. Using this approach, an inexpensive implementation on an electric wheelchair is presented. Experimental results within three structured scenarios and comparative performance using an Extended Kalman Filter (EKF) and Camera-Space Particle Filter (CSPF) implementations are discussed. The CSPF was found to be more precise in the pose of the wheelchair than the EKF since the former does not require the assumption of a linear system affected by zero-mean Gaussian noise. Furthermore, the time for computational processing for both implementations is of the same order of magnitude.

Stiffness Boundary Conditions for Critical Damping in Balance Recovery

This paper presents the analysis of a third-order linear differential equation representing the control of a muscle-tendon system, during quiet standing. The conditions of absolute stability and critical damping are analyzed. This study demonstrates that, for small oscillations, when the gravitational effect is modeled as a destabilizing negative stiffness and muscle-tendon stiffness is positive, the energy required to reach a critically damped state is very high. The high energy consumption is a consequence of a specific high threshold of muscle-tendon stiffness needed to achieve critical damping.An approximated graphical method confirms that during a hold and release paradigm intended to perturb quiet standing, the ankle response to fall recovery is proper of a third-order system. Furthermore, a direct estimation of the muscle and tendon parameters was obtained.Copyright

COMBINING GENETIC ALGORITHMS AND EXTENDED KALMAN FILTER TO ESTIMATE ANKLE'S MUSCLE-TENDON PARAMETERS

This work proposes a set of simulation and experimental measurements to estimate muscle biomechanical parameter during human quiet standing. Understanding the mechanisms involved in postural stability is indispensable to improve the knowledge of how humans can regain balance against possible disturbances. Postural stability requires the ability to compensate the movement of the body’s center of gravity caused by external or internal perturbations. This paper describes the implementation of a hybrid parameter-estimation approach to infer the features of the human neuro-mechanical system during quiet standing and the recovery from a fall. The estimation techniques combines a genetic algorithm with the State-Augmented Extended Kalman Filter. These two algorithms running sequentially are utilized to estimate the musculo-skeletal parameters. This paper shows results of the approach when representing human standing as either a second-order or third order mechanical model. Experimental validation on a human subject is also presented.Copyright

Vision-based Control of a Delta Parallel Robot via Linear Camera-Space Manipulation

One of the open problems to control a parallel robot in real-time is the larger number of parameters to be incorporated in the control model when compared to serial robots. This paper presents an innovative vision-based method to control a delta-type parallel robot based on Linear Camera-Space Manipulation. The proposed method is a simple and robust technique capable of achieving real-time control of robots without relying on the calibration of either the robot or the environment parameters. To document the robustness of this technique, a sensitivity analysis was performed in simulation where the effect of two sources of error on the end-point positioning are considered. Such sources are the variability of each link’s parameters, and the uncertainty of the visual measurements. Experimental results on a Clavel’s delta parallel robot show that end-point positioning errors obtained with Linear Camera-Space Manipulation are less than 1.5 mm, demonstrating a low sensitivity to parameter uncertainty in qualitative agreement with the simulation results. The results show that the developed approach is advantageous to control parallel robots for industrial applications in real-time and can obviate to a number of open problems common with the control of parallel robots.

Time-based identification of human ankle impedance via Microsoft Kinect

This paper presents an affordable platform to estimate human ankle mechanical impedance. This platform uses Microsoft Kinect version 2 as the motion capture system of choice and a hybrid algorithm to estimate the biomechanical parameters. The algorithm is based on the combination of an Extended Kalman filter and a Genetic Algorithms. The information provided by Kinect together with the ankle biomechanical parameters can be utilized to estimate the dynamic behavior of the recovery from falls. To prove the precision of the 3D measurements obtained with Kinect a comparison with a visual system, based on two industrial cameras was performed. Both systems were calibrated tracking the end-effector position of an industrial robot. The hold and release (H&R) experimental paradigm was used to estimate the ankle mechanics on seven subjects. The results show that Kinect v2 is a reliable motion capture device to study the neuro-mechanical response of recovering from falling.

A Case Study of Conceptual Design Analysis of Stove Brackets Using Finite Element Method

Advanced engineering techniques for analysis are modern tools used for companies to enhance the design and manufacturing cycles of new or existing products. Finite element method has become one of the most used tools in the design process of products. This paper presents a case study regarding a design change of the brackets that support the gas jet in stoves. Using the finite element method, the mechanical performance of the existing brackets is compared with the performance of the new proposed bracket. This comparison is used to evaluate the feasibility of carrying out the design change. The benefit of the new design is a reduction of materials, production costs and production times. Experimental analysis of the materials and the validation of the finite element solutions were also performed. The results of the experimental analysis and FEM simulation are discussed and presented. Finally, the performance of the existing and the new brackets under several load cases is compared and the results suggest that the product design change is feasible.Copyright