Project

# Title Team Members TA Documents Sponsor
3 WHEELED-LEGGED BALANCING ROBOT
Best Overall Project
Gabriel Gao
Jerry Wang
Zehao Yuan
design_document1.pdf
final_paper1.pdf
photo1.jpg
photo2.png
presentation1.pdf
proposal2.pdf
video
# WHEELED-LEGGED BALANCING ROBOT

## Team Members:
- Gabriel Gao (ngao4)
- Zehao Yuan (zehaoy2)
- Jerry Wang (runxuan6)

# Problem

The motivation for this project arises from the limitations inherent in conventional wheeled delivery robots, which predominantly feature a four-wheel chassis. This design restricts their ability to navigate terrains with obstacles, bumps, and stairs—common features in urban environments. A wheel-legged balancing robot, on the other hand, can effortlessly overcome such challenges, making it a particularly promising solution for delivery services.

# Solution

The primary objective of this phase of the project is to demonstrate that a single leg of the robot can successfully bear weight and function as an electronic suspension system. Achieving this will lay the foundation for the subsequent development of the full robot.

# Solution Components

## Subsystem 1. Hybrid Mobility Module:

Actuated Legs: Four actuator motors (DM-J4310-2EC) power the legged system, enabling the robot to navigate uneven surfaces, obstacles, and stairs. The legs also functions as an advanced electromagnetic suspension system, quickly adjusting damping and stiffness to ensure a stable and level platform.

Wheeled Drive: Two direct drive BLDC (M3508) motors propel the wheels, enabling efficient travel on flat terrains.

**Note: 4xDM4310s and 2xM3508 motor can be borrow from RSO: Illini Robomaster** - [Image of Motors on campus](https://github.com/ngao4/Wheel_Legged_Robot/blob/main/image/motors.jpg)

The DM4310 has a built in ESC with CAN bus and double absolute encoder, able to provide 4 nm continuous torque. This torque allows the robot or the leg system to act as suspension system and carry enough weight for further application. M3508 also has ESC available in the lab, it is an FOC ESC with CAN bus communication. So in this project we are not focusing on motor driver parts. The motors would communicate with STM32 through CAN bus with about 1 kHz rate.

## Subsystem 2. Central Control Unit and PCB:
An STM32F103 microcontroller acts as the brain of the robot, processing input from the IMU through SPI signal, directing the motors through CAN bus. The pcb includes STM32F103 chip, BMI088 imu, power supply parts and also sbus remote control signal inverter.
Might further upgrade to STM32F407 if needed.

Attitude Sensing: A 6-axis IMU (BMI088) continuously monitors the robot's orientation and motion, facilitating real-time adjustments to ensure stability and correct navigation. The BMI088 would be part of the PCB component.

## Subsystem 3. Testing Platform
The leg will be connected to a harness as shown in this [sketch](https://github.com/ngao4/Wheel_Legged_Robot/blob/main/image/sketch.jpg). The harness simplifies the model by restricting the robot’s motion in the Y-axis, while retaining the freedom for the robot to move on the X-axis and jump in the Z-axis. The harness also guarantees safety as it prevents the robot from moving outside its limit.

## Subsystem 4. Payload Compartment (3D-printed):
A designated section to securely hold and transport items, ensuring that they are protected from disturbances during transit. We will add weights to test the maximum payload of the robot.

## Subsystem 5. Remote Controller:
A 2.4 GHz RC sbus remote controller will be used to control the robot. This hand-held device provides real-time control, making it simple for us to operate the robot at various distances. Safety is ensured as we can set a switch as a kill switch to shutdown the robot in emergency conditions.

**Note: Remote controller model: DJI DT7, can be borrow from RSO: Illini Robomaster**

The remote controller set comes with a receiver, the output is sbus signal which is commonly used in RC control. We would add an inverter circuit on pcb allowing the sbus signal to be read by STM32.
Note: When only demoing the leg function, the RC controller may not be used.

## Subsystem 6. Power System
We are considering a 6s (24V) Lithium Battery to power the robot. An alternative solution is to power the robot through a power supply using a pair of long wires.

# Criterion For Success

**Stable Balancing:** The robot (leg) should maintain its balance in a variety of situations, both static (when stationary) and dynamic (when moving).

**Cargo Carriage:** The robot(leg) can be able to carry a specified weight (like 1lb) without compromising its balance or ability to move.

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**If we are able to test the leg and function normally before midterm, we would try to build the whole wheel legged balancing robot out. It would be able to complete the following :**

**Directional Movement:** Via remote control, the robot should move precisely in the desired direction(up and down), showcasing smooth accelerations, decelerations, and turns.

**Platform Leveling:** Even when navigating slopes or uneven terrains, the robot should consistently ensure that its platform remains flat, preserving the integrity of the cargo it carries. Any tilt should be minimized, ideally maintaining a platform angle variation within a range of 10 degrees or less from the horizontal.

**Position Retention:** In the event of disruptions like pushes or kicks, the robot should make efforts to return to its original location or at least resist being moved too far off its original position.

**Safety:** During its operations, the robot should not pose a danger to its surroundings, ensuring controlled movements, especially when correcting its balance or position. The robot should be able to shut down (safety mode) by remote control.

Active Cell Balancing for Solar Vehicle Battery Pack

Tara D'Souza, John Han, Rohan Kamatar

Featured Project

# Problem

Illini Solar Car (ISC) utilizes lithium ion battery packs with 28 series modules of 15 parallel cells each. In order to ensure safe operation, each battery cell must remain in its safe voltage operating range (2.5 - 4.2 V). Currently, all modules charge and discharge simultaneously. If any single module reaches 4.2V while charging, or 2.5V while discharging, the car must stop charging or discharging, respectively. During normal use, it is natural for the modules to become unbalanced. As the pack grows more unbalanced, the capacity of the entire battery pack decreases as it can only charge and discharge to the range of the lowest capacity module. An actively balanced battery box would ensure that we utilize all possible charge during the race, up to 5% more charge based on previous calculations.

# Solution Overview

We will implement active balancing which will redistribute charge in order to fully utilize the capacity of every module. This system will be verified within a test battery box so that it can be incorporated into future solar vehicles.

Solution Components:

- Test Battery Box (Hardware): The test battery box provides an interface to test new battery management circuitry and active balancing.

- Battery Sensors (Hardware): The current battery sensors for ISC do not include hardware necessary for active balancing. The revised PCB will include the active balancing components proposed below while also including voltage and temperature sensing for each cell.

- Active Balancing Circuit (Hardware): The active balancing circuit includes a switching regulator IC, transformers, and the cell voltage monitors.

- BMS Test firmware (Software): The Battery Management System requires new firmware to control and test active balancing.

# Criterion for Success

- Charge can be redistributed from one module to another during discharge and charge, to be demonstrated by collected data of cell voltages over time.

- BMS can control balancing.

- The battery pack should always be kept within safe operating conditions.

- Test battery box provides a safe and usable platform for future tests.