OdometryRobot (HAL) v1.0.0

Project Overview

OdometryRobot is a mobile robotics project focused on precise motion control and odometry estimation using a bare-metal STM32 microcontroller.

The robot executes a sequence of high-level movement commands (distance and angle) and reconstructs its trajectory using encoder-based odometry .

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Example of Input Commands

The robot receives a sequence of movement instructions such as:

Forward : 100 m
Right   : 90°
Forward : 100 m
Right   : 90°
Forward : 100 m
Left    : 90°

Demo videos

Using this sequence, the robot generates a trajectory and continuously estimates its position, orientation, and velocity through odometry.

System Architecture

The system is divided into two main parts: Hardware and Control System.

Hardware

Motors with Encoders

• Provide wheel rotation feedback
• Used for velocity and distance estimation

Microcontroller

• STM32G0 as the main MCU

• HAL

• Responsible for:

  • Real-time motor control
  • Odometry computation
  • Control system

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STM32 Software Design

All drivers and control modules are implemented using HAL

Encoder Module

• Quadrature decoding using hardware timers (encoder mode)
• Measures wheel speed and traveled distance

UART Module

• Bare-metal UART implementation
• Used for command reception and data transmission

Clock and System Configuration

• RCC and system clock configuration
• Peripheral initialization without HAL

Motor Control Module

• PWM generation using timers
• Direction and speed control of DC motors

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Control Algorithms

Position and Angular PID Control

The robot utilizes a dual cascaded PID architecture, featuring separate control loops for linear position and angular orientation. This structure improves stability, smoothness, and tracking accuracy.

Position Control Cascade

• Outer Loop (Position PID):

  • Controls the absolute target position (distance)
  • Computes the desired linear velocity setpoint

• Inner Loop (Linear Velocity PID):

  • Regulates the wheel-driven linear velocity
  • Ensures smooth motion and accurate distance tracking

This cascade structure allows the robot to reach target distances precisely while avoiding abrupt speed changes.

Angular Control Cascade

• Outer Loop (Angle PID):

  • Maintains the desired heading angle
  • Generates an angular velocity reference

• Inner Loop (Angular Velocity PI):

  • Regulates rotational speed
  • Minimizes oscillations and overshoot during turns

This approach provides stable and smooth rotational motion, especially during sharp angle changes.

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Odometry Module

The odometry module is responsible for estimating the robot’s motion state in real time. It computes:

• Linear velocity
• Angular velocity
• Robot position (x, y coordinates)
• Robot orientation (angle in radians and degrees)
• Total distance traveled

These estimates are derived from:

• Wheel encoder measurements
• Inertial data (accelerometer and gyroscope)

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Velocity Ramping System

A critical aspect of motion control is the implementation of velocity ramping for both linear and angular velocities. This system ensures smooth acceleration and deceleration, which is essential for the following reasons:

• Prevents wheel slipping: Sudden acceleration can cause loss of traction, especially on smooth surfaces
• Reduces mechanical stress: Gradual velocity changes reduce stress on motors, gears, and mechanical components
• Improves energy efficiency: Smooth acceleration profiles consume less power than abrupt movements
• Enhances system stability: Prevents overshoot and oscillations in the control loops
• Increases position accuracy: Smooth transitions lead to more precise trajectory tracking

Ramping Strategy

The ramping system is implemented for both linear velocity (odo.v) and angular velocity (odo.w) using a two-stage approach:

1. Ramp-Limited Setpoint

   • A gradually increasing velocity limit
   • Prevents sudden jumps in commanded speed

2. Target Capping

   • Ensures commanded velocities never exceed physical or safety constraints

Achieved Results

The velocity ramping system provides:

Linear Velocity Ramping Performance:

Angular Velocity Ramping Performance:

• Smooth acceleration from rest to target velocity
• Controlled deceleration when approaching target positions
• Elimination of velocity spikes that could destabilize the control system
• Consistent performance across both linear and angular motion

for visualization i used MCUViewer link

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Pinout

LED

• Internal LED: PA5

H-Bridge (Motor Driver) TB6612FNG

Signal	Pin	Note
AIN1	PB3 (D3)	Motor direction
AIN2	PB5 (D4)	Motor direction
BIN1	PB4 (D5)	Motor direction
BIN2	PB1 (A3)	Motor direction

Enable	Pin	Timer
PWMA (Left Motor)	PC1	TIM15_CH1 (PWM)
PWMB (Right Motor)	PC2	TIM15_CH2 (PWM)

• Standby pin shoud be enabled
• VM: main power (4.5 , 13.5V )
• VCC: power for the internal logic circuiuts (2.7 , 5V ) mainly 5V

Current PWM frequency configuration is 10Khz

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Encoders

Left Encoder

• OUTB: PA8 (D7) – TIM1_CH1 (Encoder mode)
• OUTB: PA9 (D8) – TIM1_CH2 (Encoder mode)

Right Encoder

• OUTA: PC7 (D9) – TIM3_CH2 (Encoder mode)
• OUTA: PC6 – TIM3_CH1 (Encoder mode)

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UART Communication

UART3 (ESP32 Communication)

• TX: PB8
• RX: PB9

UART2

• TX: PA2
• RX: PA3

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Encoder Wiring

Wire Color	Signal
Red	Motor +
Black	Motor −
Green	GND
Blue	Vcc
Yellow	OUTA
White	OUTB

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Pinouts