MICYCLEA self-balancing electric unicycle

Andrew KadisDavid CaldecottAndrew EdwardsMatthew HaynesMiroslav JerbicRhys Madigan

Supervisor: Assoc. Prof. Ben S. CazzolatoCo-Supervisor: Dr. Zebb Prime

2

Introduction

Submitted paper focused on developing the system dynamics and simulating them

The control response of the simulated and physical systems were then compared

This presentation has a slightly different focus, concentrates on the wider Micycle system

3

Literature review

Focus Designs SBUTrevor Blackwell’s SBU

The Enicycle

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Concept development

Incorporation of steering mechanism

Extensive research into steering mechanisms

Use of a rotary damper

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Concept development (2)

Lego Mockup

Preliminary Concept Model

6

Components

Sensor

Power supply

Motor controller Motor

Microcontroller

7

Mechanical design goals

Assembly of Micycle

Damper

Spring

Fork

Chassis assembly

Steeringmechanism

Perspexcovers

Protectiverubber

8

Major mechanical components Chassis assembly

Simple plate chassis design Protective Perspex covers Protective rubber

Fork design Rotary damper drive Offset centre for motor Dual bearing design Chromoly steel

Chassis plate assembly

Plate chassis

Perspex covers

Protective rubber

Fork

Damper drive

Bearing locations

Offset centre

9

Steering mechanism

Uses a torsion spring and rotary damper Makes the Micycle much easier to ride Allowed steering angle ±15˚

Steering mechanism

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Mechanical design approach

Initial desig

n CoG

Analysis

Iterate design

Drafting

Structural

analysis

ANSYS Workbench

ProE

Manufacture

11

Electrical system overview

IMU

MOTORCONTROLLER

MICRO-CONTROLLER

PERIPHERALS

HUB MOTOR

BATTERY

DISTRIBUTIONBOARD

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Controller design

Self-Balancing Unicycle

Mechanical

System

Control

ElectricalSystem

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Controller structure

PD controller structure used Derivative signal taken directly from the

IMU rather than differentiated to minimise latency in the sensor readings

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System Dynamics

The Lagrangian approach of deriving the system dynamics was applied

The dynamics were derived in terms of: φ – the rotation of the frame

about the z-axis θ – the rotation of the wheel

relative to the z axis Full details can be found in

the paper Developed simulation in

Simulink from these dynamics

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Controller benchmarking - methodology

Needed a methodology to produce repeatable results to benchmark control system

Attached a PD controller with same gains to simulated dynamics

Constrained the wheel Point of comparison between

physical and simulated control systems to examine response to disturbances

Micycle with the wheel constrained

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Controller benchmarking - results

Response of simulated system released from 30º

Response of physical system released from 30º

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Software functionality

Core

Peripheral

Safety

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Fall

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Failure modes and effect analysis (FMEA)

Comprehensive, iterative process

System engineering tool

Both a high and low level FMEA performed

Over 100 different cases considered

Full FMEA is approx. 30 pages long

Effect

Cause

Mitigating

Strategies

Failure Mode

Andrew Kadis - Software

Safety

Control

Safety

Error codes7

Safety Trip 7 Segment Error CodeBattery drained 0

Vehicle speed too fast 1Excessive current through motor 2Pitch position outside safe range 3

Angular velocity too fast 4General operational failure in the Maxon 5

ADC outside expected bounds 6IMU did not initialise correctly 7

Maxon did not initialise correctly 8IMU - abnormal power rating 9IMU - RS232 pin disconnected A

IMU - parity check failed BIMU - indeterminate communication error C

22

Project outcomes

Designed, tested and built the Micycle

A fully rideable self-balancing electric unicycle which can be learnt to ride in 30 minutes to an hour

Comprehensive iterative FMEA process completed

8 hour battery life Significant exposure to the

wider community

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Community exposure

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Community exposure (2)

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Future work

Use of a more powerful motor controller to reduce the chances of actuator saturation

Implementation of a model based controller

Incorporation of active control in the roll direction

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Questions

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