Ernesto Rodriguez-Leal

Kinematics and Dynamics of a New 16 DOF Humanoid Biped Robot with Active Toe Joint

Humanoid biped robots are typically complex in design, having numerous Degrees-of-Freedom (DOF) due to the ambitious goal of mimicking the human gait. The paper proposes a new architecture for a biped robot with seven DOF per each leg and one DOF corresponding to the toe joint. Furthermore, this work presents close equations for the forward and inverse kinematics by dividing the walking gait into the Sagittal and Frontal planes. This paper explains the mathematical model of the dynamics equations for the legs into the Sagittal and Frontal planes by further applying the principle of Lagrangian dynamics. Finally, a control approach using a PD control law with gravity compensation was recurred in order to control the desired trajectories and finding the required torque by the joints. The paper contains several simulations and numerical examples to prove the analytical results, using SimMechanics of MATLAB toolbox and SolidWorks to verify the analytical results.

Kinematics and workspace-based dimensional optimization of a novel haptic device for assisted navigation

ABSTRACT This article presents the development of a multi-point force feedback device, composed of five mechanisms that each provide a two degree-of-freedom (DOF) haptic feedback for every finger for a total of 10 DOF. This work investigates the theoretical workspace of a human index finger and uses a two DOF 7-bar linkage mechanism that is synthesized based on such a workspace. This research determines the closed-form solutions to the forward and inverse position, and presents a prototype that is built and tested as a proof of concept of the novel device. The workspace of the constructed mechanism is compared with theoretical models in order to assess their similarity and the feasibility of accelerometers as position-sensing instruments is also tested. Two sets of experiments test the performance of the mechanism and its reliability as a human–machine interface. Firstly, an operator successfully navigates an unmanned aerial vehicle avoiding an obstacle as force replaces audiovisual feedback. In the second experiment, the operator searches a chemical source using an unmanned ground vehicle, where chemical gradient is transmitted to the user as force signals.

Decoupled Closed-Form Solution for Humanoid Lower Limb Kinematics

This paper presents an explicit, omnidirectional, analytical, and decoupled closed-form solution for the lower limb kinematics of the humanoid robot NAO. The paper starts by decoupling the position and orientation analysis from the overall Denavit-Hartenberg (DH) transformation matrices. Here, the joint activation sequence for the DH matrices is based on the geometry of a triangle. Furthermore, the implementation of a forward and a reversed kinematic analysis for the support and swing phase equations is developed to avoid matrix inversion. The allocation of constant transformations allows the position and orientation end-coordinate systems to be aligned with each other. Also, the redefinition of the DH transformations and the use of constraints allow decoupling the shared DOF between the legs and the torso. Finally, a geometric approach to avoid the singularities during the walking process is indicated. Numerical data is presented along with an experimental implementation to prove the validity of the analytical results.

Screw-System-Based Mobility Analysis of a Family of Fully Translational Parallel Manipulators

This paper investigates the mobility of a family of fully translational parallel manipulators based on screw system analysis by identifying the common constraint and redundant constraints, providing a case study of this approach. The paper presents the branch motion-screws for the 3-RC-Y parallel manipulator, the 3-RCC-Y (or 3-RRC-Y) parallel manipulator, and a newly proposed 3-RC-T parallel manipulator. Then the paper determines the sets of platform constraint-screws for each of these three manipulators. The constraints exerted on the platforms of the 3-RC architectures and the 3-RCC-Y manipulators are analyzed using the screw system approach and have been identified as couples. A similarity has been identified with the axes of couples: they are perpendicular to the R joint axes, but in the former the axes are coplanar with the base and in the latter the axes are perpendicular to the limb. The remaining couples act about the axis that is normal to the base. The motion-screw system and constraint-screw system analysis leads to the insightful understanding of the mobility of the platform that is then obtained by determining the reciprocal screws to the platform constraint screw sets, resulting in three independent instantaneous translational degrees-of-freedom. To validate the mobility analysis of the three parallel manipulators, the paper includes motion simulations which use a commercially available kinematics software.

Instantaneous Kinematics Analysis via Screw-theory of a Novel 3-CRC Parallel Mechanism

This paper presents the mobility and kinematics analysis of a novel parallel mechanism that is composed by one base, one platform and three identical limbs with CRC joints. The paper obtains closed-form solutions to the direct and inverse kinematics problems, and determines the mobility of the mechanism and instantaneous kinematics by applying screw theory. The obtained results show that this parallel robot is part of the family 2R1T, since the platform shows 3 DOF, i.e.: one translation perpendicular to the base and two rotations about skew axes. In order to calculate the direct instantaneous kinematics, this paper introduces the vector mh, which is part of the joint velocity vector that multiplies the overall inverse Jacobian matrix. This paper compares the results between simulations and numerical examples using Mathematica and SolidWorks in order to prove the accuracy of the analytical results.

Kinematic and Workspace-Based Synthesis of a 2-DOF Mechanism for Haptic Applications

This paper presents the development of a mechanism aimed to haptic applications. The basic design proposed in this work is intended to interact with a finger without the use of a fixture attached to the body. This work investigates the theoretical workspace of a human index finger and proposes a two degree-of-freedom 7-bar linkage mechanism that is synthesized based on such workspace. The paper determines the closed-form solutions to the forward and inverse position, and presents a prototype that is built and tested as a proof of concept of the novel device. The workspace of the constructed mechanism is compared with theoretical models in order to assess their similarity and the viability of accelerometers as position sensing instruments is also tested.

A Study of the Instantaneous Kinematics of the 5-RSP Parallel Mechanism Using Screw Theory

This paper presents a detailed study of the instantaneous kinematics of the 5-R SP parallel mechanism with centralized motion. The study uses screw theory to investigate the mobility and the singular configurations of the mechanism. The constraint-screw set of the platform is obtained from an analysis of the motion-screw sets comprised by each kinematic chain. The analysis shows that the platform has a screw motion, that is, a one degree-of-freedom motion consisting of a rotation and a translation about an invariant axis. The motion-screw sets are also used to obtain the Jacobian matrix of the mechanism which provides closed-form solutions for the inverse and forward instantaneous kinematic problems. This matrix also provides insight into the singular configurations by investigating the constraint-screws and the motion-screws of the platform in these configurations. Finally, two numerical examples and a motion simulation of the mechanism are presented to illustrate the significance of the analytical results.

Inverse Modeling of Human Knee Joint Based on Geometry and Vision Systems for Exoskeleton Applications

Current trends in Robotics aim to close the gap that separates technology and humans, bringing novel robotic devices in order to improve human performance. Although robotic exoskeletons represent a breakthrough in mobility enhancement, there are design challenges related to the forces exerted to the users’ joints that result in severe injuries. This occurs due to the fact that most of the current developments consider the joints as noninvariant rotational axes. This paper proposes the use of commercial vision systems in order to perform biomimetic joint design for robotic exoskeletons. This work proposes a kinematic model based on irregular shaped cams as the joint mechanism that emulates the bone-to-bone joints in the human body. The paper follows a geometric approach for determining the location of the instantaneous center of rotation in order to design the cam contours. Furthermore, the use of a commercial vision system is proposed as the main measurement tool due to its noninvasive feature and for allowing subjects under measurement to move freely. The application of this method resulted in relevant information about the displacements of the instantaneous center of rotation at the human knee joint.

Haptic feedback and visual servoing of teleoperated unmanned aerial vehicle for obstacle awareness and avoidance

Obstacle avoidance represents a fundamental challenge for unmanned aerial vehicle navigation. This is particularly relevant for low altitude flight, which is highly subjected to collisions, causing property damage or even compromise human safety. Autonomous navigation algorithms address this problem and are applied in various tasks. However, this approach is usually overshadowed by unreliable results in uncertain environments. In contrast, human pilots are able to maneuver vehicles in complex situations, in which an algorithm would no offer a reliable performance. This article explores a novel configuration of assisted flying and implements an experimental setup in order to prove its efficacy. The user controls an unmanned aerial vehicle with a force feedback device, where simultaneously an assisted navigation algorithm can manipulate this apparatus to divert the unmanned aerial vehicle from its path. Experiments confirm the authors’ hypothesis that the unmanned aerial vehicle is deviated or maintains the same course at the operator’s will. Unlike conventional controllers that dictate roll, pitch, and yaw, this implementation uses direct mapping between the position represented by the haptic device and the unmanned aerial vehicle. This configuration applies feedback before the unmanned aerial vehicle has reached the position referenced by the haptic device, providing valuable time for the user to make the necessary path correction.

Demand Management Based on Model Predictive Control Techniques

Demand management (DM) is the process that helps companies to sell the right product to the right customer, at the right time, and for the right price. Therefore the challenge for any company is to determine how much to sell, at what price, and to which market segment while maximizing its profits. DM also helps managers efficiently allocate undifferentiated units of capacity to the available demand with the goal of maximizing revenue. This paper introduces control system approach to demand management with dynamic pricing (DP) using the model predictive control (MPC) technique. In addition, we present a proper dynamical system analogy based on active suspension and a stability analysis is provided via the Lyapunov direct method.