In recent decades, mobile robotics have become one of the fastest growing research fields. Compared with wheeled and tracked robots, legged robots can step over obstacles and traverse unstructured terrains. This thesis focuses on two main tasks for supporting the development of a quadruped robot, i.e., the robot embedded system design and the joint motion control. To develop the robot embedded system fulfilling the technical requirements, a controller board using an ARM-based STM32 microcontroller is designed. First, we select the key components properly, according to the practical requirements and the marketing research. Then the onboard hardware architecture is proposed, and the circuit schematic diagrams for all the functional modules are designed. The specifications and a comparison of two versions of PCBs are also presented and analyzed. Based on the designed embedded system, the actuators and sensors are tested, and selected to set up the robot experimental platform. Moreover, the firmware is configured, and the software is developed to control the position and velocity of the motors. Furthermore, the moving average filter (MAF) based cascaded PID control algorithm is designed, and is implemented to manipulate the robot joints. The experimental results demonstrate the effectiveness of the proposed control method. / Graduate

O presente trabalho visa à modelagem e ao controle ótimo de um robô quadrúpede autônomo. Devido a variações na topologia e nos graus de liberdade do robô ao longo do seu movimento, duas abordagens diferentes de modelagem foram consideradas: na primeira, foi considerado o robô com pelo menos duas pernas suportando seu corpo ou plataforma e, na segunda, considerou-se o modelo de uma perna no ar. Em ambos os casos, apresentou-se a solução dos problemas cinemáticos de posição direta e inversa por meio da parametrização de Denavit-Hartenberg. Analisaram-se também os problemas cinemáticos de velocidade e suas singularidades através da Matriz Jacobiana, e ainda obtiveram-se os modelos dinâmicos do sistema utilizando-se o Principio do Trabalho Virtual e o método iterativo de Newton-Euler para a plataforma e as pernas, respectivamente. A partir destes modelos dinâmicos, desenvolveu-se um algoritmo de otimização das perdas de energia elétrica dos motores das juntas. Neste sentido, utilizou-se a estratégia do controle independente por junta. Estratégia esta que, junto com a discretização no tempo do modelo do sistema, permitiu transformar o problema inicial de otimização para cada junta em outro de Programação Quadrática bem mais simples de ser resolvido. Depois de resolver estes problemas, para levar em conta as interações entre as dinâmicas das várias juntas, procedeu-se à busca de um ponto fixo ou mínimo global que caracterizasse a energia total gasta no movimento do sistema. Finalmente, realizada a demonstração e a análise de convergência do algoritmo, este foi testado no controle da andadura (gait) do robô Kamambaré. Como resultado do teste, observou-se o bom desempenho da formulação e a viabilidade de sua implementação em sistemas reais. / The present work aims the modeling and optimal control of an autonomous quadruped robot. Due to variations in the topology and the degree of freedom of the robot during its motion, two different modeling approaches were considered: firstly, the robot was considered with at least two legs supporting its body or platform and, second one, was considered the model of a leg in the air. In both cases, was presented the solution of the direct and inverse kinematic problem of position through the Denavit-Hartenberg parameterization. Were analyzed also, the kinematic problem of speed and the singularities through the Jacobian matrix, and was also obtained the dynamic model of the system using the Principle of Virtual Work or the dAlembert method and the iterative Newton-Euler method for the platform and legs, respectively. From these two dynamic model, were developed an algorithm for optimizing the power losses of the motors that driven the joints. In this sense, was used the strategy of independent control for each joint. Such a strategy, along with the discretization in time of the system model, has helped to change the initial optimization problem for each joint in a Quadratic Programming Problem, more simpler to solve. After solving these problems, and to take into account the interactions between the dynamics of various joints, was proceeded to search for a fixed point or a global minimum that would characterize the total energy spent in moving for the system. Finally, held the demonstration and analysis of convergence of the algorithm was tested in the control of gait of the Kamambaré robot. As a result of the test, we observed the good performance of the formulation and the feasibility of its implementation in real systems.

O presente trabalho visa à modelagem e ao controle ótimo de um robô quadrúpede autônomo. Devido a variações na topologia e nos graus de liberdade do robô ao longo do seu movimento, duas abordagens diferentes de modelagem foram consideradas: na primeira, foi considerado o robô com pelo menos duas pernas suportando seu corpo ou plataforma e, na segunda, considerou-se o modelo de uma perna no ar. Em ambos os casos, apresentou-se a solução dos problemas cinemáticos de posição direta e inversa por meio da parametrização de Denavit-Hartenberg. Analisaram-se também os problemas cinemáticos de velocidade e suas singularidades através da Matriz Jacobiana, e ainda obtiveram-se os modelos dinâmicos do sistema utilizando-se o Principio do Trabalho Virtual e o método iterativo de Newton-Euler para a plataforma e as pernas, respectivamente. A partir destes modelos dinâmicos, desenvolveu-se um algoritmo de otimização das perdas de energia elétrica dos motores das juntas. Neste sentido, utilizou-se a estratégia do controle independente por junta. Estratégia esta que, junto com a discretização no tempo do modelo do sistema, permitiu transformar o problema inicial de otimização para cada junta em outro de Programação Quadrática bem mais simples de ser resolvido. Depois de resolver estes problemas, para levar em conta as interações entre as dinâmicas das várias juntas, procedeu-se à busca de um ponto fixo ou mínimo global que caracterizasse a energia total gasta no movimento do sistema. Finalmente, realizada a demonstração e a análise de convergência do algoritmo, este foi testado no controle da andadura (gait) do robô Kamambaré. Como resultado do teste, observou-se o bom desempenho da formulação e a viabilidade de sua implementação em sistemas reais. / The present work aims the modeling and optimal control of an autonomous quadruped robot. Due to variations in the topology and the degree of freedom of the robot during its motion, two different modeling approaches were considered: firstly, the robot was considered with at least two legs supporting its body or platform and, second one, was considered the model of a leg in the air. In both cases, was presented the solution of the direct and inverse kinematic problem of position through the Denavit-Hartenberg parameterization. Were analyzed also, the kinematic problem of speed and the singularities through the Jacobian matrix, and was also obtained the dynamic model of the system using the Principle of Virtual Work or the dAlembert method and the iterative Newton-Euler method for the platform and legs, respectively. From these two dynamic model, were developed an algorithm for optimizing the power losses of the motors that driven the joints. In this sense, was used the strategy of independent control for each joint. Such a strategy, along with the discretization in time of the system model, has helped to change the initial optimization problem for each joint in a Quadratic Programming Problem, more simpler to solve. After solving these problems, and to take into account the interactions between the dynamics of various joints, was proceeded to search for a fixed point or a global minimum that would characterize the total energy spent in moving for the system. Finally, held the demonstration and analysis of convergence of the algorithm was tested in the control of gait of the Kamambaré robot. As a result of the test, we observed the good performance of the formulation and the feasibility of its implementation in real systems.

This bachelor project in mechatronics aimed to design and build a versatile robot that can both roll and walk using four legs. Control of the robot’s movement was to be achieved by a joystick, with the ability to alter direction in both rolling and walking mode. However, due to time constraints, the rolling algoritm was not implemented. Nevertheless, the final prototype achieved the ability to transform between a ball and a quadruped robot and move in four directions. The accuracy and precision of the walking sequences were evaluated and demonstrated moderate precision and a suboptimal level of accuracy. / Detta kandidatprojekt i mekatronik syftade till att designa och bygga en mångsidig robot som både kan rulla och gå med fyra ben. Kontroll av robotens rörelse ska uppnås med joystick, med möjligheten att ändra riktning i både rillande och gångläge. Men på grund av tidsbrist implementerades inte rullalgorithmen. Ändå uppnådde den slutliga prototypen förmågan att tranformera mellan en boll och en fyrbent robot och röra sig i fyra riktningar. Noggrannheten och precisionen i gångsekvenserna utvärderades och visade måttlig precision och en suboptimal nivå av noggrannhet.

There are a lot of quadruped robots in the world, but few are omnidirectional. Therefore this thesis describes the production and design process of such a robot. Examining earlier quadruped robots determined that a central microcontroller is required to control it, and servo motors are used to power the robots joints. Reaserch also determined the base of the mathematical methods used. Additionally, there are multiple types of sprawling gaits, ranging from statically stable to dynamically stable. In this project astatically stable gait is used. The thesis illustrates the mathematical models used to define the omnidirectional movement, and describes the code used to implement it. The result is a robot that can move omnidirectionally, both normally and upside down. The results show that there is a deviation depending upon the direction, but it is small. The main advantage of omnidirectionallity is the ability to change movement direction without stopping or turning. It also enables directional adjustment without requiring any steps. / Det här projektet gick ut på att skapa en krypande fyrbent robot som kan gå i alla riktningar utan att rotera runt sitt eget centrum. Det finns idag redan ett stort antal olika fyrbenta robotar, men få kan gå i alla riktningar. Därav så beskriver den här rapporten framtagningen och designprocessen för en sådan robot. Undersökning av fyrbenta robotar visade att en mikrokontroller är nödvändigför att kontrollera roboten och servomotorer bör användas för att driva lederna. Förstudeierna gav även basen för de matematiska modellerna som används for rörelserna, samt vetskapen om ett flertal olika typer av gångstilar, allt från statiskt stabil till dynamiskt stabil. I det här projektet beskrivs de matematiska modellerna som används för att definiera rörelsen i alla riktningar och hur dessa appliceras i programmeringen av roboten. Resultatet blev en robot som kan gå i alla riktningar utan att rotera runt sitt centrum, både normalt och uppochner. Detta ger möjligheten att byta rörelse riktning utan att behöva stanna eller vända sig, samt möjliggör även riktnings korrektioner utan att kräva extra steg.

Successful development of mechatronic systems requires a combination of targeted hardware and software design. The compact rescue robot (CRR), a quadruped pneumatically-actuated walking robot that seeks to use the benefits garnered from pneumatic power, is a prime example of such a system. This thesis discusses the development and testing of a simulation that will aid in further design and development of the CRR by enabling users to examine the impacts of pneumatic actuation on a walking robot. However, development of an entirely new dynamic simulation specific to the system is not practical. Instead, the simulation combines a MATLAB/Simulink actuator simulation with a readily available C++ dynamics library. This multi-platform approach results in additional incurred challenges due to the transfer of data between the platforms. As a result, the system developed here is designed in the fashion that provides the best balance of realistic behavior, model integrity, and practicality. An analytically derived actuator model is developed using classical fluid circuit modeling together with nonlinear area and pressure curves to model the valve and a Stribeck-Tanh model to characterize the effects of friction on the cylinder. The valve model is designed in Simulink and validated on a single degree-of-freedom test rig. This actuator model is then interfaced with SrLib, a dynamics library that computes dynamics of the robot and interactions with the environment, and validated through comparisons with a CRR prototype. Conclusions are focused on the final composition of the simulation, its performance and limitations, and the benefits it offers to the system as a whole.

This report will cover the work involved in building a quadruped robot which should to a certain extent resemeble a four-legged mammal. The introduction will present information related to what has inspired the project, purpose/aim, specifications, limitations and research questions. Most important in the introduction are probably the purpose/aim and research questions. Mainly, the goal was to have the robot be able to self-balance and later also be able to walk to some degree if possible. The first research question concerns how well a PID controller would affect the stability of the robot and the second question is about answering if referencing a fourlegged mammal is a good idea when building a quadruped robot. Theory and methods were combined and written as one chapter. This way relevant information could be provided in the appropriate places as the method for creating the robot was described. The chapter dives into the primary parts of the robot which are the choice of components, construction, inverse kinematics and last but not least the code including the implementation of a PID. The results show that PID regulation improves stability and performance, but PI regulation actually performed the best. Furthermore, the question regarding referencing a four-legged mammal remains inconclusive even though the model was sufficient for the task.