‘Wheeled Autonomous Mobile Robot Programming in Practice’ reading note: Part 1 Wheeled Robot Basics

'Wheeled Autonomous Mobile Robot Programming in Practice' is the title of a book by Li De that was published in 2022.


Wheeled Robot Basics


Wheeled Robot moves by wheels, driven by electric motors, controlled by controllers like STM32 or Raspberry Pi. It needs electric motor drivers like L298N.

Design a wheeled robot:
1. Planning: uses tools like FreeMind to make clear requirements (Robot dimensions, functions, work environments, special requirements).
2. Steering structure:
   a. Differential steering: use different speed on left and right motors to turn.
   b. Independent servo steering: use a servo to change direction of motors.
   Differential steering is prefered: simple, can in-place turn.
   Need a odometry motion model (based on the speed of the motors) to calculate current pose (x, y, θ).
   Needs IMU sensor to calibrate.
3. Electric motor selection
   12V power. To support odometry motion model, needs speed measurement encoder.
    So select JGA25-370-35.5k:  GA370 with speed measurement encoder (6 wires), 12V, no-load speed 170 r/min, rated-load speed 130 r/min, rated current 0.5A, max torque 3.3 KG. CM.
4. Motor driver
    a. L298N: peak current 3A, work current 2A.
    b. TB6612FNG PCB driver: work current 1.2A, peak current 2A.
5. Controller
    STM32 to control motor in real-time. It uses PWM input to catch motor speed.
    Raspberry Pi for complex functions like wifi connection, camera, sensors. Raspberry Pi isn't suitable to control motor directly, it's IO port can have up to 20ms delay.
6. Chassis
    a. Flat Chassis: Design and manufacture (acrylic plate or aluminum alloy plate)
    b. Storage bin Chassis: use a 41cm x 28cm x 23cm (16 inch x 11 inch x 9 inch) storage bin

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