Robots are known for their different power units for the movement. I built a bot with four special mecanum wheels. Robots using mecanum wheels are able to drive in any direction on the ground. Such a bot is able to strafe from one side to another, to drive a circle, back/forward, turn on the spot or just a curve. Each wheel needs a separate dc motor which is controlled independent to each other. To control the DC motors I installed a Raspberry Pi computer in my robot. I wrote the Python programs I need to control the bot by myself.
To control the four DC motors separately I installed two motor drivers from the type L298N in my robot-car. This design enables me to control each motor separately with the Raspberry Pi and the self-written Python programs. The following picture shows the robot with the two motor drivers in the back (right) of the robot.
Build your own robot car with the Raspberry Pi!Step by step to your own robot car
This book guides you in two parts through the project phases with the aim of building an individual, autonomously driving robot car. In the first part of the book you will learn the basics of robotics and the interaction of hardware, electricity and software. You build the chassis and wire the individual components - details can be found in the appropriate, richly illustrated chapters. An introduction to software installation and programming with Scratch and Python completes the first part. You do not need any previous knowledge in robotics and programming. In the second part of the book, you will familiarize yourself with the sensors required for autonomous driving. With the acquired knowledge you can individualize and further develop your robot car as you wish. The knowledge you acquire in this book will enable you to implement your own projects with the Raspberry Pi.
This book offers you that:
- Simply get into robotics with the Rasperberry Pi without prior knowledge
- Numerous illustrations, tables, circuit diagrams
- Information boxes with useful tips also for other Raspberry Pi projects
- Project code with syntax highlighting
- Two car projects: remote-controlled robot car via WLAN and self-driving car
- Hardware tips and recommendations for suitable accessories - Extensive project material as download: Raspbian image, parts list, chassis artwork and code
- Special features: Easy and robust cabling, use of high-precision time-of-flight laser distance measurement sensors, introduction to servo motors and suitable servo controllers, control via gamepad, use of an OLED display
Ingmar Stapel studied computer engineering and is currently working internationally as IT project manager and enterprise technical architect; in addition, he has been intensively involved with Raspberry Pi and robotics for years. He likes to share this knowledge with interested people from the tinkering scene at meet-ups on robotics. On his private blogs he also writes about many current technology trends.
Controlling the mecanum Raspberry Pi robot:
To control the bot I wrote two Python programs. The first one is developed to control the two motor drivers installed in the bot. The second one reads the inputs form the user and controls the movement of the bot like the direction and the speed of the robot-car. Both programs together are enabling the user to control the robot.
Very difficult is the steering of the bot during driving along a curve and then change the direction and let the robot strafe maybe to the left. The user has to change the steering by changing the speed of each dc motor and the program has to manage the transition from a curve movement to a strafe movement of the bot. The nice part of this difficult driving maneuver is that you do not have to change your hardware setup. The only thing you have to do is to change your program because all the movements are controlled from a Python program.
Everybody who wants to see the program could donwload the program from my website.
VIDEO MECANUM ROBOT:
The video shows the first tries to let the robot strafe from one side to another. It is not too easy because of the manual steering with the keyboard. Please don’t be surprised if the result of my driving maneuver is not perfect at all.
Raspberry Pi robot-car component list:
If I could awaken you interest how to build such a robot with a Raspberry Pi computer as central controlling unit you will find a list of components on my blog to help you. The component list is an overview of electronic components or ready to assemble kits which I used by myself and which I could recommend with good conscience. I used most of the components in my own projects and checked the functionality and compatibility with a Raspberry Pi.
This is the link to the component list: component list
The mecanum wheels just do not only look interesting, they enable the bot to drive special driving maneuvers which are not possible with normal wheels. To develop the Python program to control the robot with the mecanum wheels was not easy. After a few reflections how the control program could look like I started with the development. After a few training round in my office the mecanum car makes a lot of fun.