Design and control of an Autonomous Hexapod

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Dr. Stumpf Péter Pál
Department of Automation and Applied Informatics

In our civilization, the idea of wheeled locomotion is rooted so deeply, that we rarely think of any other form of ground transportation, although we are surrounded by the biological examples of legged animals, and even ourselves. Since a large portion of the Earth’s surface is inaccessible for wheeled, or even tracked vehicles, legged vehicles and robots can indeed be an invaluable asset in a number of difficult tasks.

The goal of this project was to design and build a hexapod, a six-legged robot which, due to its relative simplicity can easily gain ground in everyday and industrial applications. The final project is the documentation of this process, from choosing the materials for the robot’s body to controlling the movement of the robot.

The body was designed in CAD software, with the aim the robot to be sturdy, yet mobile. The whole mechanism was produced and assembled by hand. The main disadvantage of hand production is the low precision of the product, which makes it necessary to individually correct them.

The kinematic models of the legs of the robot were set up considering the legs as 3-DOF robotic arms. The gait for the robot was design after the example of ants and other insects. These arthropods have the so-called alternating tripod gait, meaning that at any given time, three out of their six legs touch the ground, forming a stable tripod. Given the gait and the inverse kinematic model, a simulation of one of the legs was created in LabVIEW.

To produce the appropriate voltage for the servo motors and the microcontroller, a step-down DC/DC converter was designed, along with voltage regulator circuits. These circuits were implemented in a printed circuit board. The board also conveys the control signals from the microcontroller.

The robot is controlled with a STM32 Nucleo microcontroller in conjunction with a PCA9685 PWM driver. This is necessary because the microcontroller can only produce four independent PWM signals, but each servo motor requires a separate control signal.

The robot was built and controlled with the designed gait successfully. This however, does not mean the end of the project, as such a robot can always be developed further with more complex gaits or with the use of sensors.


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