Rafael R. Torrealba

Towards the development of knee prostheses: review of current researches

Purpose – The aim is to set a state‐of‐the‐art in scientific research towards the development of knee prostheses for transfemoral amputees, by reviewing the literature in the field and by identifying different scientific research lines that have brought out through the years. Also, to provide the information about possible outcomes in the near future, and their links to cybernetics, given the present trends in the field.Design/methodology/approach – Literature related to scientific research carried out up‐to‐date in the field of knee prostheses, is reviewed in scientific articles, books and electronic sources. Then, different research lines are identified from the obtained information, and finally classified as presented in this work.Findings – Three scientific research lines regarding the development of knee prostheses were found, each one dealing with: the design of knee prostheses; the performance assessment of these prostheses; and the creation of control strategies for these prostheses which use elec...

Development of a low cost inertial measurement unit for UAV applications with Kalman Filter based attitude determination

This paper presents the development of an inertial measurement unit (IMU) specially designed for unmanned aerial vehicles (UAV) applications. The design was intended to be a low cost solution of high performance for robotic applications using 3-axis accelerometers and 3-axis gyroscopes MEMS sensors. We present simultaneous sampling to avoid the loss of orthogonality of the inertial measurements due to multiplexed data acquisition commonly used in low cost IMUs, as well as anti-aliasing processing. The IMU was implemented in two boards to separate the sensors from the processing hardware in order to be able to use it with different sets of sensors. The sensor fusion algorithm for attitude determination is based on the Kalman Filter. As testing process, the IMU was installed in a 2-DOF helicopter and the results were compared with those obtained from the encoders for the pitch and roll angles. We also present the results of the IMU installed in a T-REX 450 scale helicopter inside a motion analysis laboratory, using a custom-design safety stand that supports the helicopter allowing only its rotational 3-DOF (roll, pitch and yaw movements). Those demanding experiences tested the IMU performance under true UAV conditions and the results exhibited a maximum RMS error of 4°.

Through the development of a biomechatronic knee prosthesis for transfemoral amputees: Mechanical design and manufacture, human gait characterization, intelligent control strategies and tests

This paper presents the development of a biomechatronic knee prosthesis for transfemoral amputees. This kind of prostheses are considered ‘intelligent’ because they are able to automatically adapt their response at the knee axis, as a natural knee does. This behavior is achieved by characterizing the amputees gait through the signals captured with instrumentation of a prosthesis, which provides feedback about its current state along the gait cycle and therefore responds with the corresponding control action. In this case, unlike other commercially available intelligent knee prostheses, gait cycle characterization is based on accelerometers signals processed by an events detection algorithm. Two intelligent control strategies are presented: a bio-inspired approach, that consists of using a central pattern generator to generate a knee angle reference to be followed by the prosthesis during walking, and an adaptive scheme, that applies a control action proportional to the knee angle according to an auto-adaptive parameter dependant on gait speed. The mechanical design of the prosthesis is also presented, showing the knee joint mechanism and part of the manufacturing process. Results obtained from walking tests with both able body and amputees are shown, demonstrating the positive performance of the prosthesis in several aspects. Future works aimed at a finished product are also stated.

Cybernetic knee prosthesis: application of an adaptive central pattern generator

Purpose – The purpose of this paper is to generate a virtual knee angle reference to be followed by a knee prosthesis control, using an adaptive central pattern generator (CPG). Also, to study the feasibility of this approach to implement a continuous control strategy on the prosthesis.Design/methodology/approach – A CPG based on amplitude controlled phase oscillators (ACPOs) to track the current percentage of gait cycle on the prosthesis is proposed. Then, the virtual knee angle reference is generated along gait cycle, by interpolation with the corresponding angle of a sound knee. The structure and coupling of the CPG, as well as the control strategy are presented.Findings – The coupling of the CPG with real gait on the prosthesis was proven, regardless of gait speed. Also, it was found that the maximum knee angle reached during walking is proportional to gait speed. Finally, generation of virtual knee angle reference to be followed by a prosthesis is demonstrated.Research limitations/implications – As o...

Generalized Bilateral MIMO Control by States Convergence with time delay and application for the teleoperation of a 2-DOF helicopter

Bilateral Control by States Convergence is a novel and little exploited control strategy that has been successfully applied to the teleoperation of robotic manipulators using SISO control. Based on the state space representation, the main philosophy of this control strategy consists in achieving convergence of states between the master and the slave, by setting the dynamical behavior of the master-slave error as a states-independent autonomous system. This paper presents a generalization of this strategy to MIMO systems, with time delay in the master-slave communication channels. It is demonstrated how the feedback gains required by the state convergence control schema can be found by solving a set of ((m × n) + (m × m) + n ) nonlinear equations for a system with m inputs, n states and m outputs. Unlike previous research, which has been applied only to manipulators considering 1-DOF for the states-convergence control loop, the extension to the general MIMO case has allowed to apply the technique to the teleoperation of a 2-DOF helicopter. A decoupling network and states-feedback are used for local control, while the states-convergence control manages the bilateral issues. Simulation results are presented, showing a satisfactory performance of the control strategy.

Low-Cost Kit of Plastic Modular Adaptors for External Transtibial Prostheses

There is a very large need for prosthetic components in developing countries, where such devices are imported and prohibitively expensive. This work explores the possibility of developing and manufacturing prosthetic components locally in Venezuela while preserving high quality and function. We aimed at developing a kit of plastic modular adaptors for external transtibial prostheses. The project covers design, stress analyses, and function assessment of the components. Design criteria were established from the state-of-the-art of prosthetic adaptors in commercial models and international patents. The resulting kit comprises four adaptors of simple design. Their response was studied with stress analysis, using the finite element method, applying static loads for different instants of gait during the stance phase. The simulation of the adaptors shows that the stresses presented for a person weighing up to 980 N (100 kg) do not reach the yield strength of nylon 6.6. Then, five kits of adaptors were manufactured with this thermoplastic material using conventional metal-working machines. The resulting components are lighter and cheaper than equivalent imported metallic ones. The kits were adapted to four patients and assessed via gait analysis and questionnaire. A very good function is observed, with neither significant difference in most of spatiotemporal gait parameters compared to normal values p 0.05 nor significant asymmetries between prosthetic and sound sides. From the questionnaire, stiffness, maneuverability, and comfort ability of the manufactured kits was found high by all the patients. A 3 months adaptation period was also completed by the patients prior to performing the gait analyses. This period is considered a first field trial of the adaptors; however, these results will be complemented in the future, as the kits were not tested to structural fatigue. DOI: 10.1115/1.4003436

Comparison of CPG topologies for bipedal gait

A Central Pattern Generator (CPG) is a network of neurons capable of producing oscillatory signals without oscillatory inputs. This paper proposes of gait generator for lower lumbar exoskeleton, based on neurophysiological principles. In this manner, based in an Amplitude Controlled Phase Oscillator (ACPO) implementation for a CPG, acting as trajectory generator in normal gait for hip and knee joints of a lower lumbar exoskeleton. Three types of topologies are evaluated to determine the most suitable for this system. The results indicated that the “A” topology exhibits a smoother reaction to perturbations, which is desirable for a safe and comfortable human-machine interaction. It is also proposed as future work, the evaluation of the trajectories generator in the exoskeleton model and control.

Conceptual design of a polycentric knee prosthesis for transfemoral amputees in Venezuela

This research is aimed to establish the conceptual design of a knee prosthesis for transfemoral amputees in Venezuela. A state-of-the-art review was carried out and interviews with users were performed in order to state the design criteria. Taking these into account, the concept of the prosthetis was based on a voluntary control four-bar linkage prosthetic knee mechanism. This provides stability during the initial contact and stance, as well as ability to initiate voluntary flexion toward late stance before the toe-off. As for the alignment of the prosthesis, the orientation angle on the lower limb was found to be a very important parameter to bear in mind, given its incidence in the location of the instantaneous center of rotation of the mechanism (anterior or posterior) with respect to the ground reaction force vector during walking.

Development of Cortex®-to-OpenSim file transfer platform for motion capture-based dynamic simulation of biomechanical models

The human gait is one of the most important movements for the development of the human being life. It represents a sequence of synchronized movements of the joints and muscles activations of the lower limbs. The knowledge of how those movements are performed, taking into account the biomechanical foundations and the physiology of the elements involved, is very important in order to be able to identify certain pathologies and make comparisons between them and normal gait for particular parameters. One way of studying the gait kinematics and kinetics is through a gait analysis. A gait analysis allows to determining the spatio-temporal location of markers placed in landmarks of the body subject in study using cameras and sensors. In the Center for Motion Analysis of the Simón Bolívar University it is used the software Cortex® to editing and processing this captured data. The aim of this work is to develop a platform for transferring these files from Cortex® into the open-source software OpenSim for performing further dynamic analyses.

Design and Performance of Plastic Modular Adaptors for External Transtibial Prostheses

There is a very large need for prosthetic components in developing countries, where such devices are imported and prohibitively expensive. The present work explores the possibility of developing and manufacturing prosthetic components locally in Venezuela, preserving high quality and function. We aimed to develop a kit of plastic modular adaptors for external transtibial prostheses. The project was divided in four stages that covered design, stress analyses, manufacture, and function assessment of the components. The design process is presented in detail, resulting a prototype that comprises four adaptors of simple design. Their response was studied with stress analysis using the Finite Element Method applying static loads for different instants of gait during the stance phase. Then, five kits of adaptors were manufactured with thermoplastic material using conventional metal-working machines. The resulting components were lighter and cheaper than equivalent imported metallic ones. The kits were adapted to four patients and assessed via gait analysis. A very good function was observed, with no significant differences in spatio-temporal gait parameters (p<0.05) compared to normal values nor significant asymmetries between prosthetic and sound sides. However, these results are preliminary as the kits were not tested to structural fatigue. This remains for a future work aimed to assess the performance of such adaptors in the field.