In this section, we give a brief introduction to the chassis structure of the mobile robot, and focus on the composition structure of the basic version of FishBot.
For a mobile chassis, there are two core functions to be provided — perception and execution capabilities, which we will introduce separately.
Hardware development platform
The so-called perception is the ability to obtain environmental information by giving sensors. In mobile robots, the sensors we commonly use are
• Distance sensors — radar, ultrasound• Wheel speed sensor — coder• Inertial measurement cell — IMU sensor• Image sensors — monocular, binocular, depth cameras
In addition to the above categories, you can also mount other sensors you need according to your needs, such as temperature and humidity measurement sensors.
For the basic version of FishBot, there are four kinds of sensors on board: radar, ultrasonic, code and IMU.
We have already used ultrasound and IMU in the previous article, so in this section we will briefly introduce the two sensors of radar and coder.
1.1 Lidar
The lidar we use is a single-line rotating triangulation lidar.There is a lidar transmitter and a linear CCD receiver in the lidar header.
1.2 odom coder
In the mobile robot, we need to obtain the rotational speed of each wheel of the robot in real time, convert the speed of the wheel into the speed of the robot according to the kinematic model of the robot, and get the walking distance of the robot by integrating the speed (speed * distance).
The sensor we use to measure the speed of the wheel is the coder, and on the FishBot, we use the AB electromagnetic coder.
Electromagnetic coder is composed of 1 and 2 two Hall sensors and a circular magnet 3 together, the magnet is a magnetic margin distribution, the magnet is fixed on the rotor of the motor, when the motor rotates, drive the magnet to rotate, at this time for detecting the magnetic Hall sensor will detect changes in the magnetic, so that you can measure the motor in a certain period of time to rotate the number of turns that is the motor speed.
Actuator
The so-called actuator is the part responsible for moving. In a mobile robot, the most important actuator is the motor. In addition, we can also regard the OLED display device as an actuator that can be operated.
We use a 370 gear motor with a rated voltage of 12V on our FishBot, with a rated speed of 130 rpm, a rated current of 0.5A, and a torque of 600 centimeters.
I believe you are familiar with the motor, so what is a geared motor? A geared motor refers to a motor with a reducer.
The motor is generally composed of a stator and a rotor, and generally rotates faster, but the output torque is relatively small. Therefore, we will equip the motor with a reducer to reduce the speed and increase the torque.
Other accessories
In addition to actuators and sensors, there are also some necessary accessories
- Battery, providing power support
- Voltage regulator module, providing voltage conversion
- Necessary support structures such as universal wheels
All supporting materials and tutorials of FishBot.
0. FishBot learning process
1. FishBot hands-on assembly tutorial
2. Introduction and download of configuration assistant
3. Main control board firmware burning and configuration
4. Use ROS2 keyboard to control FishBot
5. Radar firmware burning and configuration
6. Radar drive and mapping test
7. FishBot-Nap2 navigation test
Extension 1: FishBot matching radar drive tutorial (source code version)
Extension 2: The method of using micros agent to drive the main control board on raspberry pie
Expansion 3: FishBot Raspberry Pie Configuration Map Building Navigation
FishBot Camera Series
[FishBotCamera] 1. Firmware download and configuration
[FishBotCamera] 2. Drive FishBotCamera and try to adjust parameters
[FishBotCamera] 3. Realize detection with YOLO
2、 FishBot Real Machine Development Series Tutorial (from lighting to navigation)
2.1 Basic Part — Introduction to Embedded Development and Environment Construction
1. What is MCU
2. Microprocessor development platform
3. Build the PlateFormIO development environment
4. PIO engineering structure&construction method
5. The first HelloWord project
6. Serial communication — receiving experiment
2.2 Introduction — Start from lighting up
1. Lighting basics — understand LED drive circuit
2. Complete lighting GPIO control
3. Learn to use the key GPIO input
4. Battery voltage measurement — learn to use ADC
2.3 Advanced Chapter — Learn to Use the Third Party Library
1. Learn how to install the third-party library
2. Use open source library to drive IMU
3. Learn object-oriented programming — encapsulate IMU driver
4. Use open source library to drive OLED
5. Communication Protocol Classroom — I2C Communication
6. I2C communication experiment — lighting OLED
2.4 Introduction and installation of MicoRos
1. MicroROS introduction and service installation
2. Your first MicroROS node
2.5 Introduction — topic and service communication on embedded platform
1. Topic subscription — control LED
2. Topic release — upload electricity information
3. Service Implementation — Add Two Numbers
2.6 Advanced Chapter — Advanced Principles and Use of MicoROS
1. Custom message interface
2. Make a clock system time synchronization
3. Understand the transmission principle — replace the protocol
4. Drying performance — MicroROS with dual core operation
2.7 ROS2 hardware actual combat (self-made simple radar)
1. Introduction to simple radar principle
2. Use ultrasonic to measure distance
3. Learn to use actuator by controlling steering gear
4. Steering gear+ultrasonic cycle scanning
5. Visual point cloud radar message synthesis
2.8 Construction of FishBot control system
1. Introduction to mobile robot chassis structure
2. Start with H-bridge — introduction of motor drive principle
3. Motor control forward and reverse rotation test
4. Speed control experiment of motor control
5. Use of open source library for motor control to drive multiple motors
6. Make a remote control car — subscribe to ROS2 Twist
7. Start with encoder — Introduction to speed measurement principle
8. Pulse measurement and calibration experiment
9. Speed conversion — robot maximum speed measurement
10. Control speed — PID controller realization
11. Introduction to kinematics of two wheel differential robot
12. Real time velocity calculation forward kinematics solution
13. Target speed control — inverse kinematics
14. Odometer calculation — speed integration
15. Release odometer with MicroROS
16. Project summary and expansion
17. Extension — Source Code Compilation Agent
2.9 Drawing practice of FishBot SLAM
1. Visual radar point cloud — learn to drive radar
2. Preparation before drawing construction 1- Understanding ROS standard REP105
3. Preparation before drawing construction 2- Publish Odom’s TF
4. Preparation before drawing construction 3- Preparation of URDF
5. Use SLAM_TOOLBOX to complete drawing construction
6. Map saving and editing
2.10 Implementation of FishBot navigation
1. Introduction and installation of Navigation 2
2. Configure Navigation 2 parameters
3. Write Launch and start navigation
4. Single point and waypoint navigation