Development of walking robot using compliance mechanism

Walking robot is a trend in this 21st century as Industrial Revolution 4.0 which involved automation has become a hot topic. Unlike ordinary moving robots, walking robots that take humans and animals as references can move on unpaved surfaces. Compliance mechanism is a flexible mechanism that transfers input force into output force through plastic deformation of certain members in the structure. A compliant structure can be classified as a monolithic structure that deforms elastically without any joint or linkage between the members. Unlike motorised robot legs requiring an input motion in each joint and link, a single input force can operate a compliant leg. Therefore, this research aims to develop a 3D printed compliant leg. This project is challenging because there is no reference for the single-piece compliant leg development using Three-Dimensional(3D) printing technology. The application of Jansen Linkage in the development of the compliant leg also results in difficulties because there is no standard equation for the calculation of each member in the Jansen Linkage. Hence, the development of the Jansen Linkage using different dimensions will solve these problems by varying the difference occurring upon changing the dimension. We also make Finite Element Analysis (FEA) of the product. The thesis will be supported by the walking motion pattern, force vs time graph and FEA analysis results for the product

Geometric optimization of a self-adaptive robotic leg

RÉSUMÉ: En utilisant une approche similaire aux mécanismes de doigts sous-actionnés, les capacités d’adaptation d’une architecture de jambe robotique à deux DDL de type Hoeckens-Pantographe sont optimisées dans cet article afin de lui permettre de surmonter des obstacles imprévus lors de sa phase de vol. Une optimisation multiobjective des paramètres géométriques du mécanisme a été effectuée afin de mettre en évidence l’opposition existant entre deux objectifs contradictoires et choisir un compromis. Le premier de ces objectifs mesure la capacité d’adaptation passive de la jambe en calculant le couple d’entrée requis pour amorcer le glissement désiré le long d’un obstacle. La deuxième fonction objective évalue la trajectoire de base suivie par l’extrémité de la jambe en se basant sur trois critères : linéarité, ratio de la phase de support, et rapport hauteur / largeur. En comparaison avec la géométrie initiale pasée sur le mécanisme de Hoecken, le mécanisme final trouvé sur le front de Pareto présente une amélioration marquée des capacités d’adaptation, au coût d’une légère réduction de la durée de la phase de support. Cet article étend la philosophie de l’autoadaptation mécanique, qui a récemment beaucoup attiré l’attention dans le domaine de la préhension, à celui de la marche, et ouvre la voie à une validation expérimentale de cette approche. ---------- ABSTRACT: This paper demonstrates the self-adaptive capabilities of a two-degree-of-freedom Hoeckens-pantograph robotic leg (inspired by underactuated mechanical fingers) as well as its optimization, allowing it to overcome unexpected obstacles during its swing phase. A multi-objective optimization of the mechanism’s geometric parameters is performed using a genetic algorithm to highlight the trade-off between two conflicting objectives and select an appropriate compromise. The first of those objective functions measures the leg’s passive adaptation capability through a calculation of the input torque required to initiate the desired sliding motion along an obstacle. The second objective function evaluates the free-space trajectory followed by the leg endpoint using three criteria: linearity, stance ratio, and height-to-width ratio. In comparison with the initial geometry based on the Hoecken’s linkage, the selected final mechanism chosen from the Pareto front shows an important improvement of the adaptation capabilities, at the cost of a slight decrease in the stance phase duration. This paper expands on mechanical self-adaptive design philosophy, which has recently attracted a lot of attention in the field of grasping, to legged locomotion and paves the way for subsequent experimental validation of this approach

Desarrollo de sistema de locomoción y odometría en un robot móvil para navegación en espacios no uniformes

Proyecto de Graduación (Licenciatura en Ingeniería Mecatrónica) Instituto Tecnológico de Costa Rica. Área Académica de Ingeniería Mecatrónica, 2020Se presenta el desarrollo de un prototipo de robot de exploración para ambientes no uniformes, como parte del proyecto de investigación PROE, en una colaboración de la escuela de matemática y el área académica de ingeniería en mecatrónica, ambas del Tecnológico de Costa Rica. Dentro de las características físicas del mismo se cuenta con una masa de 504.2 g y unas dimensiones máximas de 241.8 mm x 169.0 mm x 151.82 mm. Se construyó con técnicas de manufactura como impresión 3D y corte láser, así como la utilización de piezas estándar. Se planteó la utilización de una suspensión rígida tipo rocker bogie implementado con una barra diferencial. El mismo posee una capacidad de superar obstáculos con ángulos de elevación de 40˚ con un 100% de éxito, además de desenvolverse adecuadamente en superficies pedregosas. El costo estimado del robot corresponde a $231. Se plantean los algoritmos de control del robot utilizando un controlador de tipo PI independiente en cada una de las ruedas, cuya variable de interés es la velocidad lineal de cada una de las ruedas. La odometría del mismo se descompuso en avances y giros, con un error relativo promedio en la velocidad menor al 1.58Se utilizó una fusión de sensores IMU, Magnetómetro y codificadores para determinar la orientación y la posición en las tres dimensiones. Se demuestra que la fusión de sensores entre el filtro de Madgwick y los codificadores permiten la determinación de la orientación alrededor del eje z con un error relativo del 0.58The characteristics of the robot are a mass of 504.2 g, the dimensions are 241.8 mm x 169.0 mm x 151.82 mm. It is built with manufacturing techniques like 3D impression, laser-cut, and standard pieces. A rocker-bogie rigid suspension is used with a differential bar. The robot is capable of overcome obstacles with elevation angles of 40 with 100$231. The robot Control algorithms are presented using an independent PI controller for each wheel. The odometry is decomposed in turns and moves forward movements, with a relative error in velocity of less than 1.5%. The robustness of the controller is demonstrated in ramps and obstacles, in which it was capable of correct and maintain the velocity. Those algorithms are implemented in an STMF103C microcontroller, with highlevel functions like move forward a distance and turn some degrees. Sensor Fusion was used between the IMU, magnetometer, and encoders for determination of orientation and position in the three dimensions. It is shown that sensor fusion between the Madgwick filter and the encoders allow the estimation of the orientation around the z-axis with a relative error of less than 1.5% in turns of a 90-degree angle. Also, it presented a relative error of estimation of less than 0.45% for the position in the x and y-axis and 2.5% for the estimation of each wheel. Finally, it was able to estimate the altitude with a 1.3% error