Battery operated omnidirectional platform

Sponsors	Electrical and Computer Engineering Department
Team Name	Battery Operated Omnidirectional Platform
Duration	Spring 2021 - Fall 2021
Faculty Adviser	Dr.Law
Mentors	Dr.Law and Dr.Hess
Client	Dr.Hess
Team Members	Blaine Porter John Mackesy Taylor Leavey Qihang Liu

The goal of this project was to work with a mechanical engineering team to create a mobile RC platform for the University of Idaho Marching Band during the band’s performances.

Problem Definition

The Battery Operated Omnidirectional Platform is a continuation of the project called Band on the Run from last year. Our goal is to create a mobile platform that can be used to carry various instruments and personnel. The platform will be remotely controlled by a wireless controller and powered by rechargeable batteries.

Background

The University of Idaho Marching Band (also known as the Voice of Idaho) has over a one-hundred years of history. With hundreds of outstanding students, the band provides excellent performances for the University of Idaho sports programs and school events. In 2011, Dr. Edwin Odom, from the Department of Mechanical Engineering, and Dr. Daniel Bukvich, professor of Percussion and Music Theory, started a project to design a mobile drum set to be used during performances by the University Band, which came to be known as the Band-Beesten. This year we're improving on and finishing a new mobile platform which will be much more modular, thus allowing a greater degree of artistic freedom for the Sound of Idaho.

Deliverables

Battery operated omnidirectional platform project should operate under these specififications:

• Controlled remotely over a distance of 100 meters
• Powered by lithium based cells
• Have a total payload of 800lbs
• Provide continuous movement and operation for 15 to 20 minutes
• Translate and rotate independently from 2 different reference perspectives
• Maintain multiple modes of safety and redundancy measures to prevent malfunction or harm to riders
• Designed with environmental, global, social, and economic factors as constraints per ABET requirements

Design Considerations

Overview

Through the comprehensive consideration of the design specification of the platform, we conclude that the platform needs the following basic requirements:

System control

Energy storage

Electric motors

Remote communications

System Control

System control is an important part of the electronic system of the platform, especially the microcontroller used in the main computing unit of the system control, which includes sensors and energy storage.

Sensors

The sensors we are using in this project will allow us to get information such as speed, temperature, current, and voltage. By using encoders, accelerometers, and thermistors, we can ensure safe operation of the platform.

Energy Storage

Because the platform needs to translate and articulate about the field whilst moving about 800 pounds, including its own weight, a lot of energy is needed to propel the platform. The use of lithium batteries ensured that a higher power density could be obtained, but to use lithium batteries requires the use of a battery management system (BMS).

Considerations for choosing a BMS were:

the voltage

current

Battery Temp over use

Energy Management

The lithium cells are managed using a battery management system (BMS) described in a later section of this page. Battery pack were made using LiFePO₄ batteries. A "cell" is then constructed of 8 batteries in parallel. A full battery "pack" then was made from 8 of the "cells" placed in series. Our energy source mitigates many safety concerns associated with more traditional lithium ion chemistries.

Electric Motors

When considering a motor, we must consider torque ratings, speed ratings, current consumption, voltage and thermal characteristics in order to ensure the safety and capability of the platform.

Motor Control

With regard to motor controllers, we must consider their ability to control speed, torque and acceleration. Current and voltage are also important considerations, as the motor must withstand relatively large currents.

Remote Communications

In order to avoid interference with signals on the platform and to ensure signal integrity, the signal transmission distance had to also be considered. The typical distance considered is half of a football field (50 yards) to a maximum of the entire length (100 yards). In this manner we can ensure all possible variations of movement on a field are accounted for.

Specifications

Major Design Components

Microcontroller ESP32 Key Features High Clock Speed - 240MHz 32 bit Dual Core Processor WiFi/Bluetooth Availability 34 Software Assigned General Purpose I/O Pins

ESP32 Microcontroller

LiFePO4 cells A123 ANR26650m1-B Nomenclature Battery[ies]: Individual 3.3 VDC LiFePO4 cells, pictured to the right C Rate: Refers to charge/discharge properties. Obtained by dropping the “h” from “Ah” 1 Specifications Max Continuous Discharge: 50A Peak Discharge: 120A (10s) Max Power Density: 2600W/Kg (23°C) Cell Capacity : 2.5/2.4 Ah (@ 0.5C Rate, Nominal/ Min) Mitigates safety concerns of traditional Li-ion chemistries Less environmentally impactful Improved recyclability Wider temp stability range 1 Ex) 1C charging current for 1 battery = 2.5A

A123 ANR26650m1-B cell

LiFePO4 Battery Packs Specifications Battery Pack: Comprised of 8 Cells, made of 8 individual batteries themselves, pictured to the right. Nominal Voltage: 26.4VDC (28.8 VDC Max) Max Continuous Discharge: 400A Peak Discharge: 960A (10s) Pack Capacity : 20/19.2 Ah (Nom/Min)

Battery management system Roboteq BMS1040A Key Features Power Max Cell Pack Voltage: 40V Max Number of Cells: 10 Max Load Current: 100A(continuous), 200A(5s peak) Max Charge Current: 50A Communication RS485 USB CAN bus Proprietary PWM I/O Digital inputs: 1 Digital Outputs: 2 Temperature Sensors: 3 Mechanical Conduction Plate Cooling Dimensions: 145mm x 115mm x 23mm Weight: 250g	Roboteq BMS1040A Unit	Roboteq BMS1040A Schematic
Motor Controllers Electromen EM 282 C Key Features Power Range Supply voltage: 10-50 VDC (Nominal) Idle current typ 20 mA Output Motor Current: 100 A (Continuous)Peak 200A (5s) Braking Load Current: 50 A (continuous)Peak 100A (5s) Current limit adjustable 1-200 A	Electromen EM 282 C Motor Controller	Electromen EM 282 C Motor Controller Schematic
Motors AmpFlow E30-400-24-G Key Features 2.1 Peak HP Motors Nominal Voltage of 24 VDC Features reduction ratio of 8.3 : 1 Output Stall Torque of 64 ft-lbs Unloaded: 680 RPM and 3.2 A Output stage further reduced by 3 : 1 sprockets, resulting in total Reduction Ratio of 24.78 : 1 and an Output Shaft Stall Torque of 192 ft-lbs Omni-wheel’s diameter is 1 foot, thereby maximum unloaded speed of platform theoretically is 8.2 MPH; Max wheel translational force = (192 ft-lbs/ 0.5 ft) = 394 lbs Current rotary encoder sensors allow for 0.025 MPH resolution	AmpFlow E30-400 Gearmotor

Project Learning

Learning Goals

• The reason for design
• Systematic summary of the learned knowledge, improve the ability of comprehensive application. In the design  process, a systematic review and summary of the previous professional basic knowledge, professional knowledge, curriculum design and production practice.
• Continue to learn new knowledge, gradually improve the knowledge structure, through theory and practice, improve the ability to solve practical problems.
• Improved our teamwork and communication skills through weekly meetings, reports and discussions, through the exchange of information and ideas, help us to complete the project better.
• Cultivate our comprehensive application of the basic theory and professional knowledge of the ability to solve engineering and technical problems.

Final Design

The platform consists of four omnidirectional wheels, each driven by an electric motor that is able to rotate and move easily across the field, carries approximately 800 pounds, runs for at least 15 to 20 minutes, and is remotely controlled by an RC controller and receives commands from sensors to receive information, and is powered by a lithium battery source. The lithium cells are managed using a battery management system.

Additional Documentation

Code

https://drive.google.com/drive/folders/1xyedKqGsTjozy96BKvYeSZpPIHeirnee

Meeting Minutes

https://drive.google.com/drive/folders/1KGosfL3CM-6RcloYBeyTq2qicFHQb5os

Design Review

https://drive.google.com/drive/folders/1AKPyCWhBV05nmORdXEKZ9gJTPJg-qod6

Budget

https://drive.google.com/drive/folders/19DSChNGeVE9RLb3vltRxdsD86Fh2ls9S

Team Members

	Name: Blaine Porter Major: Electrical Engineering Hometown: Rathdrum, ID Responsibilities: Team Lead Motors and Motor Controller Subsystems LED Light Show Circuit Diagram Email: port9632@vandals.uidaho.edu or porterswelding@yahoo.com
	Name: JJ Mackesy Major: Electrical Engineering Hometown: Post Falls, ID Responsibilities: Controls System Wiki Page Support Email: mack0923@vandals.uidaho.edu
	Name: Taylor Leavey Major: Electrical Engineering Hometown: Clarkston, WA Responsibilities: Battery Management System Finances Email: leav8805@vandals.uidaho.edu
	Name: Qihang Liu (Prounounced as "chee-hong") Major: Electrical Engineering Hometown: Jiangsu Province, China Responsibilities: Wiki Page DFMEA and ABET Email: qiha4313@vandals.uidaho.edu