University of Southern California Dissertations and Theses

Dynamic power sharing for self-reconfigurable modular robots

(USC Thesis Other)

Dynamic power sharing for self-reconfigurable modular robots

PDF

Download

Open document

Flip pages

Download a page range

Download transcript

Copy asset link

Request this asset

Transcript (if available)

Content DYNAMIC POWER SHARING FOR SELF-RECONFIGURABLE
MODULAR ROBOTS

by

Chi-An Chen

A Thesis Presented to the
FACULTY OF THE USC VITERBI SCHOOL OF ENGINEERING
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(ELECTRICAL ENGINEERING)

May 2012

Copyright 2012 Chi-An Chen
ii
Acknowledgments

I would like to foremost thank my advisor Professor Wei-Min Shen for giving me a
chance to learn both hardware and software on SuperBot (Self-Reconfigurable Modular
Robot). Through the discussion with Professor Wei-Min Shen, Professor, Alexander A.
Sawchuk, Professor John Granacki, Professor Berok Khoshnevis and Computer Science
Ph.D. students: Nadeesha Ranasinghe, Chi Ho Chiu and Luenin Barrios has greatly
improved my research work and skills. Many thanks to Professor Wei-Min Shen and Dr.
Behnam Salemi for the original design of Power Sharing circuit and Dr. Akiya Kamimura
for the Power Sharing circuit construction, testing, and improvements over the original
design. I also really appreciate Luenin Barrios for helping me to film the videos of the
Power Sharing Scenarios.
Thank God and all friends at Immanuel Church very much for offering me a
wonderful study area and giving me the resolute to keep walking and studying all the
time.
I am deeply thankful to my parents, for their kindness, encouragement, support and
patience within whole my life.
iii
Table of Contents

Acknowledgments ..................................................................................................... ii
List of Tables ............................................................................................................. v
List of Figures .......................................................................................................... vi
Abstract ..................................................................................................................... x

Chapter 1: Introduction ........................................................................................ 1
1.1 Motivation ............................................................................................. 2

Chapter 2: SuperBot Rolling Track Experiment ................................................... 3

Chapter 3: Research Problem............................................................................... 5
3.1 The Various Power Consumption Problems ............................................ 5
3.2 Charging Problem .................................................................................. 6
3.3 Communication Problem ........................................................................ 7
3.4 Objective................................................................................................ 7

Chapter 4: Challenges.......................................................................................... 8
4.1 Detect the Needs and Make a Decision ................................................... 8
4.2 Challenges in a distributed manner ......................................................... 9
4.3 Related Work ....................................................................................... 10
4.3.1 Odin from University of Southern Denmark [2] ........................ 10
4.3.2 Planar Catoms from CMU [3] ................................................... 12
4.3.3 Claytronics from CMU [4] ........................................................ 13

Chapter 5: System Design ................................................................................. 15
5.1 Hardware Design ................................................................................. 17
5.2 Software Design ................................................................................... 23
5.2.1 AvrX Real Time Operation System ........................................... 23
5.2.2 BehaviorTasks .......................................................................... 24
5.2.3 SystemTasks ............................................................................. 26

iv
Chapter 6: Dynamic Power Sharing ................................................................... 28
6.1 Offering Power Scenario ...................................................................... 28
6.2 Bypass Power Scenario ........................................................................ 32
6.3 Only Receiving Power Scenario ........................................................... 37
6.4 Both Charging the Battery and Receiving Power Scenario .................... 41
6.5 Only Charging the Battery Scenario ..................................................... 45
6.6 Power Sharing Communication Protocol .............................................. 50

Chapter 7: Conclusion and Future Works ........................................................... 57
7.1 Summary and Contributions ................................................................. 57
7.2 Future Works ........................................................................................ 58
7.2.1 Large Scale ............................................................................... 58
7.2.2 Power Management .................................................................. 58
7.2.3 Power Loss When Bypassing Power ......................................... 59
7.2.4 Optimizing Power Sharing in Different Tasks ........................... 60

References ............................................................................................................... 61

v
List of Tables

Table 2-1: Average Remaining Battery Voltage (Every run was started
from a fully charged battery 8.2V.). ............................................................ 4

Table 7-1: Solutions to Potential Battery Problems. .................................. 57

.
.
.

.

vi
List of Figures

Figure 1-1: Self-Reconfigurable Modular Robots Fix Objects in the Space. 1

Figure 2-1: SuperBot in a ring form performs Rolling Track. ..................... 3

Figure 3-1: SuperBot in a biped shape. ....................................................... 5

Figure 3-2: SuperBot in a quadruped shape. ............................................... 6

Figure 4-1: SuperBot Module Appearance [5]. ........................................... 9

Figure 4-2: Overview of Odin .................................................................. 10

Figure 4-3: Odin system block diagram ..................................................... 11

Figure 4-4: The Overview of Planar Catom from CMU. ........................... 12

Figure 4-5: The Power Sharing Circuit Diagram of Planar Catom from
CMU. ....................................................................................................... 12

Figure 4-6: Claytronics Overview from CMU. ......................................... 13

Figure 4-7: Capacitive Coupling Concept Diagram. ................................. 14

Figure 4-8: Capacitive Coupling Circuit Diagram. ................................... 14

Figure 5-1: SuperBot Module Main Parts Connections [5]. ...................... 15

Figure 5-2: SuperBot Module Master Board Main Functions Block
Diagram [5]. ............................................................................................ 16

vii
Figure 5-3: SuperBot Module Slave Board Main Functions Block
Diagram [5]. ............................................................................................ 16

Figure 5-4: Hardware Topology 1............................................................. 17

Figure 5-5: Hardware Topology 2............................................................. 18

Figure 5-6: Final Power Sharing Simplified Circuit. ................................. 19

Figure 5-7: Power Sharing Switch 1 Circuit Diagram. .............................. 20

Figure 5-8: Power Sharing Switch 2 Circuit Diagram. .............................. 20

Figure 5-9: Power Sharing Switch 3 Circuit Diagram. .............................. 21

Figure 5-10: Power Sharing Switch 0 Circuit Diagram. ............................ 21

Figure 5-11: RF Receiver Circuit Diagram. .............................................. 22

Figure 5-12: Software Main Functions Block Diagram. ............................ 23

Figure 6-1: Offering Power Scenario ........................................................ 28

Figure 6-2: The 1
st
Step of Offering Power Scenario. ............................... 29

Figure 6-3: The 2nd Step of Offering Power Scenario .............................. 30

Figure 6-4: The 3rd Step of Offering Power Scenario ............................... 30

Figure 6-5: The Final Switch Status of Offering Power Scenario .............. 31

Figure 6-6: Bypass Power Scenario .......................................................... 32

Figure 6-7: The 1st Step of Bypass Power Scenario. ................................. 33

Figure 6-8: The 2nd Step of Bypass Power Scenario. ............................... 34
viii

Figure 6-9: The 3rd Step of Bypass Power Scenario. ................................ 35

Figure 6-10: The 4th Step of Bypass Power Scenario. .............................. 35

Figure 6-11: By Pass Scenario Switches Status. ....................................... 36

Figure 6-12: Only Receiving Power Scenario. .......................................... 37

Figure 6-13: The 1st Step of Only Receiving Power Scenario................... 38

Figure 6-14: The 2nd Step of Only Receiving Power Scenario. ................ 39

Figure 6-15: The 3rd Step of Only Receiving Power Scenario. ................. 40

Figure 6-16: Only Receiving Power Switches Status. ............................... 40

Figure 6-17: Both Charging the Battery and Receiving Power Scenario ... 41

Figure 6-18: The 1st Step of Both Charging the Battery and Receiving
Power Scenario. ....................................................................................... 42

Figure 6-19: The 2nd Step of Both Charging the Battery and Receiving
Power Scenario. ....................................................................................... 43

Figure 6-20: The 3rd Step of Both Charging the Battery and Receiving
Power Scenario. ....................................................................................... 44

Figure 6-21: Both Charging the Battery and Receiving Power Scenario
Switches Status. ....................................................................................... 44

Figure 6-22: Only Charging the Battery Scenario. .................................... 45

Figure 6-23: The 1st Step of Only Charging the Battery Scenario. ............ 46

Figure 6-24: The 2nd Step of Only Charging the Battery Scenario. .......... 47
ix

Figure 6-25: The 3rd Step of Only Charging the Battery Scenario. ........... 48

Figure 6-26: Only Charging the Battery Switches Status. ......................... 48

Figure 6-27: The 4th Step of Only Charging the Battery Scenario. ........... 49

Figure 6-28: Two Modular Robots Communicates. .................................. 50

Figure 6-29: Power Sharing Algorithm. .................................................... 51

Figure 6-30: The 1st Step of Power Sharing Communication Scenario. .... 51

Figure 6-31: The 2nd Step of Power Sharing Communication Scenario. ... 52

Figure 6-32: The 3rd Step of Power Sharing Communication Scenario. ... 53

Figure 6-33: The 4th Step of Power Sharing Communication Scenario. .... 54

Figure 6-34: The 5th Step of Power Sharing Communication Scenario. .... 54

Figure 6-35: The 6th Step of Power Sharing Communication Scenario. .... 55

Figure 6-36: The 7th Step of Power Sharing Communication Scenario. .... 56

x
Abstract

Self-Reconfigurable Modular Robots is one important field in the robotics research. It
can be used to deal with the unforeseen situations, fixing the distributed problems,
self-recover from damage and among others. In Chapter 1: Introduction briefly introduces
Self-Reconfigurable Modular Robots’ background and application and explains why
Self-Reconfigurable Modular Robots need Power Sharing mechanism.
Chapter 2 demonstrates the SuperBot rolling track example and explains the
importance of Power Sharing functions.
Chapter 3: Research Problem describes the problems including various power
consumption problems, charging problem, communication problem and brings out the
objective: how modular robots share power between them dynamically.
Chapter 4: Challenges lists the challenges including making a decision and
communication in a distributed manner. Three related research are discussed and
compared with the Dynamic Power Sharing Mechanism.
Chapter 5: System Design shows the whole system structure including software and
hardware. In the software part, several main functions which are used to accomplish

xi
Power Sharing Functions are introduced. In the hardware part, the hardware design
procedure and main components are discussed.
Chapter 6: Dynamic Power Sharing, six Power Sharing scenarios including 1.
Offering Power, 2. Bypass Power, 3. Receiving Power Only, 4. Charging the Battery Only,
5. Both Charging the Battery and Receiving Power and 6. Power Sharing Communication
Protocol are demonstrated to present how the Self-Reconfigurable Modular Robots share
power dynamically. The Power Sharing Communication Protocol was created in order to
help each modular robot to negotiate what kind scenario they want to adapt. The Power
Sharing Algorithm is also brought out to make the Self-Reconfigurable Modular Robots
doing Powering Sharing in a distributed manner.
Chapter 7: Conclusion summarizes the possible power problems which Power
Sharing Functions can solve. The future work including large scale, power management,
power loss, optimizing Power Sharing in different tasks is discussed.

1
Chapter 1: Introduction

Self-Reconfigurable Modular Robots are autonomous machines and created to deal with
unpredictable, dynamic and unforeseen situations, environment and tasks, e.g. discovery
on planets, building house, fixing objects in the space as shown in Figure 1-1. According
to different tasks, they can form various shapes to maximize the work efficiency of each
task.

Figure 1-1: Self-Reconfigurable Modular Robots Fix Objects in the Space.
2
1.1 Motivation
Each module needs power, therefore for the purpose of extending task operation time,
various methods have been developed, e.g. reducing components’ power consumption,
optimizing robot’s motion efficiency and among others.
Because of Self-Reconfigurable Modular Robots’ structure, each module needs to
cooperate with each other to accomplish the task. Within the task, “Power” is always an
important resource that each modular robot needs to negotiate and share with each other.
Some modular robots might consume less power than others during a certain task. In this
situation, the modular robots which consume less power can offer their own power to
others which consume more energy.
Based on this concept, the Power Sharing research between modular robots has
become an essential topic in the Self-Reconfigurable Modular Robots research. Because
Self-Reconfigurable Modular Robots have dynamic structures, the power consumption
within them is also dynamic. Therefore, in order to extend the task operation time or
achieve some specific tasks, the Power Sharing structure needs to be created dynamically
to handle all kinds of future power needs.
3
Chapter 2: SuperBot Rolling Track Experiment

Figure 2-1 shows SuperBot Rolling Track [5]: there are six modular robots connected
together. In this case, each modular robot does not have Power Sharing circuits. From the
table 2-1, the first run (970 m) was terminated due to Module 1’s low battery and the
second run (1142 m) was terminated by Module 1’s and Module 3’s low batteries.

Figure 2-1: SuperBot in a ring form performs Rolling Track.

4

Table 2-1: Average Remaining Battery Voltage (Every run was started from a fully
charged battery 8.2V.).

Based on the experiment results, solving low power problem is a significant step to
extend the operation time. In this Rolling Track Experiment, Module 1’s battery might be
malfunction. Therefore if SuperBot wants to extend its operation time, the other modules
might need to offer their power to Module 1, so that Module 1 can still work.
Self-Reconfigurable Modular Robots’ structure is dynamic, therefore, the Power
Sharing functions should be also in a dynamic structure to handle all kinds of tasks.

5
Chapter 3: Research Problem

3.1 The Various Power Consumption Problems
Due to the various shapes and different tasks of the Self-Reconfigurable Robot, the power
consumption is continuously variable and dynamic. Figure 3-1 demonstrates SuperBot
developed by USC Information Sciences Institute Polymorphic Robotics Laboratory in a
biped like shape. Figure 3-2 shows SuperBot in a quadruped shape.

Figure 3-1: SuperBot in a biped shape.
6

Figure 3-2: SuperBot in a quadruped shape.

Each shape may execute different tasks, therefore, the power needs in each module
are different, e.g. If the SuperBot in a biped shape needs to use its right hand more
frequently, the other modules might offer more power to it instead of drawing any power
from right hand module. Therefore, based on the various power consumption
characteristics, the Power Sharing Functions should be designed to be dynamic.

3.2 Charging Problem
In SuperBot, originally, each module has its own battery and without the proposed Power
7
Sharing mechanism, so each module would have to be charged separately. Based on
SuperBot structure, the Power Sharing Circuits should be designed to charge all modular
robots when they are connected together even the whole system is off.

3.3 Communication Problem
One important feature of Power Sharing Functions is that each module can determine if it
wants to share power or bypass power or do nothing, etc. Therefore, before each module
makes the decision, they need to communicate with each other. In other words, the Power
Sharing Functions on SuperBot are active and each module can negotiate its power needs
in order to achieve different tasks.

3.4 Objective
The research problem focuses on how a group of modular robots can share power among
themselves dynamically. Six Power Sharing Scenarios including 1. Offering Power, 2.
Bypass Power, 3. Receiving Power Only, 4. Charging the Battery Only, 5. Both Charging
the Battery and Receiving Power and 6. Power Sharing Communication Protocol will be
introduced.

8
Chapter 4: Challenges

4.1 Detect the Needs and Make a Decision
In the ISI SuperBot hadware structure, each module has its own battery. In the real case,
the battery might be malfunction randomly and when the situation happens, the damaged
battery module might want to get the power from the neighbor modules instead of
charging its own battery. Furthermore, due to the different situations, the modular robot
might only want to bypass the power from another module. Because each module
consists of one master board, one slave board, and six communication boards on the six
sides as shown in Figure 4-1. The other modular robots can dock and share the power
through the six sides where the communication boards exist. Besides that, SuperBot has
various shapes, e.g. ring shape, biped shape or quadruped shape, so how to coordinate the
Power needs and make a decision in order to maximize the operation time or efficiency is
a challenge.

9

Figure 4-1: SuperBot Module Appearance [5].

4.2 Challenges in a distributed manner
There is no central control in SuperBot, therefore, for Power Sharing, each module needs
to communicate in order to negotiate the power needs. A reliable communication protocol
for Power Sharing for self-reconfigurable modular robot is necessary for coordination in
a distributed manner.

10
4.3 Related Work
Power Sharing is a problem in Self-Reconfigurable Modular Robots structure. Due to the
various kinds of Self-Reconfigurable Modular Robots, different kinds of Power Sharing
structures and circuit have been developed. Three examples of the related research were
introduced in the following sections:

4.3.1 Odin from University of Southern Denmark [2]

Figure 4-2: Overview of Odin
11

Figure 4-3: Odin system block diagram

Figure 4-2 shows the overview of Odin from University of Southern Denmark. Figure 4-3
shows Odin’s Power Sharing circuit. The power trace is connected between modules.
With this structure, the Power Sharing functions cannot be dynamic, which means if one
of the batteries is malfunction, it might affect other modules.

12
4.3.2 Planar Catoms from CMU [3]

Figure 4-4: The Overview of Planar Catom from CMU.

Figure 4-5: The Power Sharing Circuit Diagram of Planar Catom from CMU.

Figure 4-4 and Figure 4-5 show Planer Catoms from CMU. The transformer is used to
transfer the power. The current is passively rectified via the H-Bridge protection diodes,
13
providing Catom B with power. Nevertheless, the circuit structure cannot be dynamic, e.g.
once Catom A has no power, it can’t bypass the power from other Catoms to Catom B.

4.3.3 Claytronics from CMU [4]

Figure 4-6: Claytronics Overview from CMU.

14

Figure 4-7: Capacitive Coupling Concept Diagram.

Figure 4-8: Capacitive Coupling Circuit Diagram.

Figure 4-6, Figure 4-7 and Figure 4-8 show the Power Transfer research of Claytronics
from CMU. The capacitors are used to transfer the power from a square wave generator.
However, just as Planar Catoms case described in the section 4.3.2, the circuit structure
doesn’t support dynamic Power Sharing.

15
Chapter 5: System Design

Figure 5-1 shows the printed circuit board connection block diagram of one SuperBot
module. Figure 5-2 and Figure 5-2 show the main function blocks of the master board
and slave board [5].

Figure 5-1: SuperBot Module Main Parts Connections [5].

16

Figure 5-2: SuperBot Module Master Board Main Functions Block Diagram [5].

Figure 5-3: SuperBot Module Slave Board Main Functions Block Diagram [5].
17
5.1 Hardware Design
Figure 5-1 shows the first version of Power Sharing circuits. The power trace and ground
trace are connected together to share the power. However, if one battery is
malfunctioning, the other batteries are also affected. E.g. if one battery is short circuit, the
others will also lose power fast. This implies that the switch in front of every battery
should be added.

Figure 5-4: Hardware Topology 1.

Therefore, the second version of Power Sharing circuits was created as shown in
Figure 5-2. Although the short circuit battery problem can be solved, once the switch is
open, the module is also dead. However, some tasks might need every module to be alive,
e.g. the rolling track task needs every module to have power, if one module has
insufficient power, the whole task fails. Besides preventing from isolating the bad battery,
18
in some situations, the whole system might also need to keep every module alive during
the tasks.
In order to solve the two problems stated above and adopt the various combinations
of Self-Reconfigurable Modular Robots, the module might open or close the switches
dynamically. Therefore, a Dynamic Power Sharing Circuit should be invented to handle
the dynamic features of Self-Reconfigurable Modular Robots.

Figure 5-5: Hardware Topology 2.

19

Figure 5-6: Final Power Sharing Simplified Circuit.

After some modifications and considerations, the Dynamic Power Sharing circuit is
created as shown in Figure 5-7. With this dynamic structure, six Power Sharing scenarios
can be demonstrated, including 1. Offering Power Scenario, 2. Bypass Power Scenario, 3.
Receiving Power Only Scenario, 4. Both Charging and Powering Scenario, 5. Only
Charging the Battery and 6. Power Sharing Communication Protocol.

20

Figure 5-7: Power Sharing Switch 1 Circuit Diagram.

Figure 5-8: Power Sharing Switch 2 Circuit Diagram.

21

Figure 5-9: Power Sharing Switch 3 Circuit Diagram.

Figure 5-10: Power Sharing Switch 0 Circuit Diagram.

Figure 5-7 shows Switch 1’s circuit. This circuit is mainly combined by the three
components: STL8NH3LL Power FET, MIC5018 High-Side MOSFET Driver and
22
2N7002 MOSFET. STL8NH3LL Power FET is used for passing high electric current
(Max. 8A). MIC5018 High-Side MOSFET Driver is used for high output voltage (around
16V). 2N7002 MOSFET is used for controlling MIC5018 High-Side MOSFET Driver to
turn on or off. MIC5018 High-Side MOSFET Driver is turned on by default so that each
module are ready to receive power any time and be turned on if other modules are will to
help.

Figure 5-11: RF Receiver Circuit Diagram.

IA4320 Universal ISM Band FSK Receiver is used to receive the turn-on signal. It
covers the unlicensed frequency bands at 315, 433, 868, and 915 MHz. The IA4320 has a
completely integrated PLL, and its rapid settling time allows for fast frequency hopping,
bypassing multipath fading, and interference to achieve robust wireless links.
23
5.2 Software Design

Figure 5-12: Software Main Functions Block Diagram.

To perform Power Sharing scenarios successfully, coordinating software and hardware
and meet real-time constraints is necessary. E.g. a motor on SuperBot needs some periods
to hold its position. If the software doesn’t offer enough “delay” to the motor, the motor
might have insufficient time to act to the right position software [1]. Figure 5-12 shows
the software main functions block diagram and the interactions between them.

5.2.1 AvrX Real Time Operation System
Real Time Operation Systems are designed to give an in-time response to the real world
24
event. Each event may have its deadline, the scheduling mechanism in the Real-Time
Operation Systems must respond before the deadline.
Setting priority is one feature of the Real-Time Operating System. The Real-Time
Operating System follows programmer's priorities strictly and executes the tasks. If the
priorities are in a wrong order, the system may result in a weird action. E.g. if the
Question Task in the SuperBot Power Sharing software code is set in the 1st priority, the
system will stop until the confirmation signal is received.
The Real Time Operation Systems have several features which are suitable for robot
design, therefore SuperBot uses AvrX which is a Real Time Multitasking Kernel written
for the Atmel A VR series of micro controllers as its operation system kernel.
Behavior tasks are used to run high-level control software and the functions they use
are provided by systems tasks. Behavior tasks cannot access to the low-level devices
directly and can only call the interfaces provided by the system tasks [1].

5.2.2 BehaviorTasks
5.2.2.1 TwistTask
This task mainly performs twist task. The modular robot’s angle is mainly used Cosine

25
function to perform. Generally speaking, for Power Sharing Scenarios, when getV oltage()
function is larger than threshold voltage, The twist task will be performed.

5.2.2.2 BlinkTask
This task handles the blue LED blink phenomenon. When getVoltage() function is
smaller than the threshold voltage, the global variable “blink” is activated (blink > 0) and
the blue LED starts to blink.

5.2.2.3 MasterSendTask
This task handles “Sending Message Task”. Once Module 1 decides to ask for help, the
“send” global variable is set to 1 and the “Ask for Help” signal can be sent out by the
infrared transmitter on the communication boards on SuperBot module. In this task, there
are three messages which can be sent: 1. Ask for Help; 2. Docking Complete; 3. Separate.
Using “IRSend” function, Module 1 can choose which communication board to send out
the message.

5.2.2.4 QuestionTask
This task is used to deal with the questions including 1. “ Ask for Help ? ” 2. “ Docking
26
Complete? ” 3. “ Separate ? ”. The global variables are activated correspond to the
confirmation signals, e.g. When the answer of “Call for help (y/n)?” is “y”, the “send”
global variable is set to 1 and “MasterSendTask” starts to send “Ask for Help” signal to
the neighbor modules.

5.2.3 SystemTasks
5.2.3.1 miscTask.c
“miscTask” is usually used to communicate between master and slave boards. There is
“SlaveMiscTask” in master board’s miscTask.c which mainly sends the message to slave
board’s “miscTask.c” and controls slave board’s actions, e.g. slave board’s LED control
of Power Sharing Scenarios:
The 1
st
Step:
When Module 2 receives the LED control message from Module 1, ModuleDiagnostic.c
in BahaviorTasks of Module 2’s master board gets the message.
The 2
nd
Step:
ModuleDiagnostic.c in BahaviorTasks of Module 2’s master board passes the message to
miscTask.c in SystemTasks of Module 2’s master board.
The 3
rd
Step:
27
The miscTask.c in SystemTasks of Module 2’s master board passes the message to
miscTask.c in SystemTasks of Module 2’s slave board.
The 4
th
Step:
When miscTask.c in SystemTasks of Module 2’s slave board receives the message, the
“setColorLED” function in miscTask.c will control the LED status on the Slave Board.

28
Chapter 6: Dynamic Power Sharing

Based on SuperBot (the Reconfigurable Modular Robot) developed by USC ISI
Polymorphic Robotics Laboratory, the Dynamic Power Sharing circuit is created as
shown in chapter 5, Figure 5-7. Six scenarios including 1. Offering Power Scenario, 2.
Bypass Power Scenario, 3. Receiving Power Only Scenario, 4. Both Charging and
Powering Scenario, 5. Only Charging the Battery and 6. Power Sharing Communication
Protocol are demonstrated. The six scenarios show how each module shares power
dynamically and also internal switches status.

6.1 Offering Power Scenario

Figure 6-1: Offering Power Scenario

29
The 1st Step:

Figure 6-2: The 1
st
Step of Offering Power Scenario.

Module 1’s blue and green LED stay on, which indicates Module 1 is in the initial state:
switch 1 and switch 3 are closed. When switch 1 is closed, it means Module 1 is ready to
receive power from the other connected modules. When switch 3 is closed, it means
Module 1’s main power is on. The green arrow and blue arrow mean it can do only
charging the insufficient power module’s battery or only offering power to the
insufficient power module or both charging the battery and offering power.
Module 1 starts to perform twist task, which means Module1 starts to head to
Module 2 and is going to offer its power to Module 2 which has no power.

30
The 2
nd
Step:

Figure 6-3: The 2nd Step of Offering Power Scenario

Figure 6-4: The 3rd Step of Offering Power Scenario

31

Figure 6-5: The Final Switch Status of Offering Power Scenario

Figure 6-3 shows Module 1 discovers Module 2 and connects together. Figure 6-4
shows Module 1 changes to Offering Power mode and the red LED stays on, which
represents switch 2 is closed and the yellow LED also stays on, which represents switch 0
is opened.
32
From Figure 6-5, the electric current goes through switch 2, through switch 0 to
Module 2’s external power trace. Module 2 gets power and starts to move again.

6.2 Bypass Power Scenario

Figure 6-6: Bypass Power Scenario

The scenario 2 demonstrates “By Pass” scenario. Figure 6-6 shows if the Bypass Power
Module doesn’t have enough power or doesn’t want to offer its power to the neighbor
modules, it performs “By Pass Scenario” and let the modules which are not directly
connected to the receiving power modules offer their power.

33
The 1st Step:

Figure 6-7: The 1st Step of Bypass Power Scenario.

Module 1’s blue and green LED stay on, which indicates Module 1 is in the initial
state: switch 1 and switch 3 are closed. When switch 1 is closed, it means Module 1 is
ready to receive power from the other connected modules. When switch 3 is closed, it
means Module 1’s main power is on.

34
The 2nd Step:

Figure 6-8: The 2nd Step of Bypass Power Scenario.

Figure 6-8 shows Module 1 stops twisting and the blue LED starts to blink, which
indicates Module 1 doesn’t have enough power (V < Vth1) to turn on Module 2. Module
1 can choose to become Bypass Power Scenario. In the Bypass Power Scenario, yellow
LED stays on, which means switch 0 is closed. The green LED disappears, which means
switch 1 is open and cannot get power from the external power trace.

35
The 3
rd
Step:

Figure 6-9: The 3rd Step of Bypass Power Scenario.

The electric current from the modules which are not directly connected to Module 2
can offer their power going through Module1’s external power trace to Module2’s
external power trace.

The 4th step:

Figure 6-10: The 4th Step of Bypass Power Scenario.

36

Figure 6-11: By Pass Scenario Switches Status.

After Module 2 receives power, it starts to perform twist task as shown in Figure
6-10. Figure 6-11 shows the Bypass Scenario switch status: switch 1 and switch 2 are
open, which means Module 1 itself can’t draw power from the other Modules. Switch 0 is
closed, which means Module 1 offers its external power path and only bypasses the
power from other Modules to Module 2.
37
6.3 Only Receiving Power Scenario

Figure 6-12: Only Receiving Power Scenario.

Figure 6-12 shows if the insufficient battery module doesn’t want to charge its own
battery, e.g. battery is malfunction, it can perform “Only Receiving Power Scenario”. The
blue arrows in Figure 6-12 mean only offer power to the insufficient battery module’s
system without charging the battery. The power source might come from the offering
power module or bypass power module.
38
The 1
st
Step:

Figure 6-13: The 1st Step of Only Receiving Power Scenario.

Figure 6-13 shows Module 1 and Module 2 perform twist task at first. Module 1’s
blue and green LED stay on, which indicates Module 1 is in the initial state: switch 1 and
switch 3 are closed. When switch 1 is closed, it means Module 1 is ready to receive
power from the other connected modules. When switch 3 is closed, it means Module 1’s
main power is on.

39
The 2nd Step:

Figure 6-14: The 2nd Step of Only Receiving Power Scenario.

Module 1 stops twisting and the blue LED starts to blink, which indicates Module 1
doesn’t have enough power (V < Vth1). So Module 2 starts to head to Module 1, which
means Module 2 is going to offer its power to Module 1. Module 1 chooses to become
“Only Receiving Power Scenario”: Switch 2 is closed (red LED stays on) and Switch 1 is
open (green LED disappears).

40
The 3rd Step:

Figure 6-15: The 3rd Step of Only Receiving Power Scenario.

Figure 6-16: Only Receiving Power Switches Status.
41
Figure 6-15 shows when Module 2 connects to Module 1 and only offers its power
(the blue arrow) to Module 1, Module 1 immediately starts to perform twist task. Because
Module 1 has low battery, the diode in Figure 6-16 doesn’t turn on, which means
Module1’s battery power doesn’t go through the diode to the whole system.

6.4 Both Charging the Battery and Receiving Power
Scenario

Figure 6-17: Both Charging the Battery and Receiving Power Scenario

42
Figure 6-17 shows if the insufficient battery module wants to charge its own battery and
also get the power simultaneously from the other modules, it can perform “Both Charging
the Battery and Receiving Power Scenario”.

The 1st Step:

Figure 6-18: The 1st Step of Both Charging the Battery and Receiving Power Scenario.

Figure 6-18 shows Module 1 and Module 2 perform twist task at first. Module 1’s
blue and green LED stay on, which indicates Module 1 is in the initial state: switch 1 and
switch 3 are closed. When switch 1 is closed, it means Module 1 is ready to receive
power from the other connected modules. When switch 3 is closed, it means Module 1’s
main power is on.

43
The 2nd Step:

Figure 6-19: The 2nd Step of Both Charging the Battery and Receiving Power Scenario.

Figure 6-19 shows Module 1 stops twisting and the blue LED starts to blink, which
indicates Module1 doesn’t have enough power (V < Vth1). If Module 2 decides to help
Module 1, it will start to enter “Offering Power Scenario”, i.e. “start to enter Offering
Power Scenario” means the switch 2 is closed, but the switch 0 is open. The switch 0 is
closed only after it connects to Module 2 in order to prevent from “spark” when the two
different voltage modules connect together. Module 2 starts to head to Module 1, which
means Module 2 is going to offer its power to Module 1.

44
The 3rd Step:

Figure 6-20: The 3rd Step of Both Charging the Battery and Receiving Power Scenario.

Figure 6-21: Both Charging the Battery and Receiving Power Scenario Switches Status.
45
Figure 6-20 shows when Module 1 and Module 2 connect together, Module 2’s
switch 0 turns on. Because every modular robot’s default state is: the switch 1 and switch
3 are closed, and the switch 2 is open, when Module 2 connects to Module 1, Module 2
charges Module 1’s battery and offer power to Module 1’s main power path
simultaneously as shown in Figure 6-21.

6.5 Only Charging the Battery Scenario

Figure 6-22: Only Charging the Battery Scenario.

46
Figure 6-22 shows if the insufficient battery module only wants to charge its own battery
without receiving power, it can perform “Only Charging the Battery Scenario”. The green
arrows in Figure 6-22 mean only charging the battery in the insufficient battery module’s
without offering power to its system. The power source might come from the offering
power module or bypass power module. This scenario is usually used during SuperBot is
in the rest mode.

The 1st Step:

Figure 6-23: The 1st Step of Only Charging the Battery Scenario.

Figure 6-23 shows Module 1 and Module 2 perform twist task at first. Module 1’s
blue and green LED stay on, which indicates Module 1 is in the initial state: switch 1 and
switch 3 are closed. When switch 1 is closed, it means Module 1 is ready to receive
47
power from the other connected modules. When switch 3 is closed, it means Module 1’s
main power is on.

The 2nd Step:

Figure 6-24: The 2nd Step of Only Charging the Battery Scenario.

Figure 6-24 shows Module 1 stops twisting and the blue LED starts to blink, which
indicates Module1 doesn’t have enough power (V < Vth1). If Module 2 decides to help
Module 1, it will start to enter “Offering Power Scenario” as stated before. Module 2
starts to head to Module 1, which means Module 2 is going to offer its power to Module
1.

48
The 3
rd
Step:

Figure 6-25: The 3rd Step of Only Charging the Battery Scenario.

Figure 6-26: Only Charging the Battery Switches Status.
49
Module 1’s switch 3 can be turned on by controlling RF transmitter and become
“Only Charging the Battery Scenario”. Figure 6-26 shows the simplified circuits which
indicate the switch 3 is open and Module 1’s battery can’t offer power to the main power
trace but the switch 1 still can be turned on by connecting Module 2. However, even the
switch 1 is closed, the green LED disappears.

The 4th Step:

Figure 6-27: The 4th Step of Only Charging the Battery Scenario.

After a while, Module 1’s battery gets enough power and disconnects from Module
2. Module1 can be restarted by the RF transmitter and start to move again.

50
6.6 Power Sharing Communication Protocol
Before each module performs the Power Sharing scenarios, they need to communicate
first to determinate which Power Sharing scenario they want to choose. Therefore, the
Power Sharing Communication Protocol is created to coordinate each
Self-Reconfigurable Modular Robot’s power needs.

Figure 6-28: Two Modular Robots Communicates.

51

Figure 6-29: Power Sharing Algorithm.

The 1
st
Step:

Figure 6-30: The 1st Step of Power Sharing Communication Scenario.
52
Figure 6-30 shows Module 1 performs twist task at first. Module 1’s blue and green
LED stay on, which indicates Module 1 is in the initial state: switch 1 and switch 3 are
closed. When switch 1 is closed, it means Module 1 is ready to receive power from the
other connected modules. When switch 3 is closed, it means Module 1’s main power is
on. In this case, Module 2 remains still for waiting for the “Ask for Help” signal.

The 2
nd
Step:

Figure 6-31: The 2nd Step of Power Sharing Communication Scenario.

Figure 6-31 shows after a while, Module 1’s battery is low (V < Vth1) and Module 1
stops twisting and the blue LED starts to blink, which indicates Module 1 doesn’t have
enough power to perform twist task.

53
The 3rd Step:

Figure 6-32: The 3rd Step of Power Sharing Communication Scenario.

Module 1 can decide if it wants to send out “Ask for Help” message or not. In this
case if Module 1 decides to choose “Both Charging the Battery and Receiving Power
Scenario” and then send out “Ask for Help” message to the neighbor module: Module 2,
The Green LED starts to blink, which means Module 1 is in “Asking for Help” status as
shown in Figure 6-32.

54
The 4th Step:

Figure 6-33: The 4th Step of Power Sharing Communication Scenario.

Figure 6-33 shows when Module 2 receives “Ask for Help” signal, the red LED
starts to blink, which means Module 2 receives “Ask for Help” message from Module 1.

The 5th Step:

Figure 6-34: The 5th Step of Power Sharing Communication Scenario.
55
Module 2 can also decide if it wants to offer the help to Module 1. If Module 2
decides to help Module 1, Module 2 starts to head to Module 1 and is going to connect to
Module 1. In the meanwhile, the red LED stays on, which means Module 2’s switch 2 is
closed and ready to perform “Offering Power Scenario”.

The 6th Step:

Figure 6-35: The 6th Step of Power Sharing Communication Scenario.

When Module 1 and Module 2 connect together, Module 2’s yellow LED stays on,
which indicates that the switch 0 turns on and Module 2 starts to offer power to Module
1.

56
The 7th Step:

Figure 6-36: The 7th Step of Power Sharing Communication Scenario.

After Module1 gets enough power, it can decide when to separate. In this case,
Module 1’s blue LED stops blinking, which means V > Vth1. If Module 1 decides to
separate from Module 2, Module 1 can send “Separate” message to Module 2. In this
case, when Module 2 gets “Separate” message, Module 1 and Module 2 separate from
each other and return to their original status.

57
Chapter 7: Conclusion and Future Works

7.1 Summary and Contributions
This thesis describes five Dynamic Power Sharing Scenarios and Power Sharing
Communication in a distributed manner. Each scenario is demonstrated on SuperBot [6]
hardware. Table 7-1 summarizes the complete solutions for the potential battery problems.
“1” means the switch is closed and “0” means the switch is open, e.g. (0, 1, 0, 1) means
the switch 0 is open, switch 1 is closed, switch 2 is open and switch 3 is closed.

Table 7-1: Solutions to Potential Battery Problems.

58
Based on the five Dynamic Power Sharing scenarios and communication protocol,
the Power Sharing Algorithm is created and can be used in some Self-Reconfigurable
Modular Robots with communication functions.

7.2 Future Works
7.2.1 Large Scale
Currently, there is only one SuperBot module with Power Sharing circuit. Therefore, the
circuit can only be tested on one module. In most cases, one task needs several
Self-Reconfigurable Modular Robots to combine together, e.g. biped shape or quadruped
shape. Therefore, enlarging the numbers of modules with Power Sharing circuit and
verifying the Power Sharing scenarios in a large scale are the next milestone.

7.2.2 Power Management
Based on the Dynamic Power Sharing experiments on SuperBot, it can be implemented
to the Power Management in an area or a country. As time goes by, the power needs are
growing and people want to find non-pollution solutions for these tremendous needs.
Therefore, power management is becoming an important topic in the current society.
59
Imaging in the future, every area has a big battery which can be charged by solar power,
wind power or any other natural, non-pollution power. Each area has the switches like
SuperBot’s Dynamic Power Sharing Circuit topology and connects with each other. Each
area has its own power production, once the area has more power production, it can offer
its own power to the less power production area. E.g. in the USA, due to the different
regions, the areas where can get more solar power might charge the areas where have less
power production. E.g. Las Vegas may offer its rich solar power to the less power
production area.

7.2.3 Power Loss When Bypassing Power
If the scale is large, then performing Bypass Power scenario continuously in a long
distance might experience power loss. Therefore, the Power Sharing circuit or the Power
Sharing Algorithm might need to be modified to prevent from the power loss caused by
Bypassing Power.
Power loss becomes more serious when the Dynamic Power Sharing Scenarios are
implemented to in a large area. Therefore, evaluating the best arrangement of battery
placement in a wide area, e.g. country, is also a future research.
60
7.2.4 Optimizing Power Sharing in Different Tasks
Self-Reconfigurable Modular Robots can become various shapes in order to execute
different tasks. Each shape might have different power consumption. Therefore, for
maximizing the system’s operation time and efficiency, how to optimize the Power
Sharing distribution is an important research in the future.

61
References

[1] Chiu, Harris; Shen, Wei-Min;, “Concurrent and Real-Time Task Management for
Self-Reconfigurable Robots,” In Proc. Third Intl. Conf. on Autonomous Robots and
Agents, 2006.

[2] Garcia, Ricardo Franco Mendoza; Lyder, Andreas; Christensen, David Johan; Stoy,
Kasper; , "Reusable electronics and adaptable communication as implemented in the
odin modular robot," Robotics and Automation, 2009. ICRA '09. IEEE International
Conference on , vol., no., pp.1152-1158, 12-17 May 2009.

[3] Karagozler, M.E.; Campbell, J.D.; Fedder, G.K.; Goldstein, S.C.; Weller, M.P.;
Yoon, B.W.; , "Electrostatic latching for inter-module adhesion, power transfer, and
communication in modular robots," Intelligent Robots and Systems, 2007. IROS
2007. IEEE/RSJ International Conference on , vol., no., pp.2779-2786, Oct. 29
2007-Nov. 2 2007.

[4] Kirby, B.T.; Aksak, B.; Campbell, J.D.; Hoburg, J.F.; Mowry, T.C.; Pillai, P.;
Goldstein, S.C.; , "A modular robotic system using magnetic force effectors,"
Intelligent Robots and Systems, 2007. IROS 2007. IEEE/RSJ International
Conference on , vol., no., pp.2787-2793, Oct. 29 2007-Nov. 2 2007.

[5] Shen, Wei-Min; Chiu, Harris; Rubenstein, Michael; Salemi, Behnam;, “Rolling and
Climbing by the Multifunctional SuperBot Reconfigurable Robotic System,” In Proc.
Space Technology and Applications Intl. Forum (STAIF-08), AIP Conference
Proceedings No. 969, American Institute of Physics, pp. 839–848, Melville, NY,
February 2008.

[6] Salemi, Behnam; Moll, Mark; and Shen, Wei-Min;, “SUPERBOT: A Deployable,
Multi-Functional, and Modular Self-Reconfigurable Robotic System,” In Proc. 2006
IEEE/RSJ Intl. Conf. on Intelligent Robots and Systems, Beijing, China, October
2006.

Abstract (if available)

Abstract Self-Reconfigurable Modular Robots is one important field in the robotics research. It can be used to deal with the unforeseen situations, fixing the distributed problems, self-recover from damage and among others. In Chapter 1: Introduction briefly introduces Self-Reconfigurable Modular Robots’ background and application and explains why Self-Reconfigurable Modular Robots need Power Sharing mechanism. ❧ Chapter 2 demonstrates the SuperBot rolling track example and explains the importance of Power Sharing functions. ❧ Chapter 3: Research Problem describes the problems including various power consumption problems, charging problem, communication problem and brings out the objective: how modular robots share power between them dynamically. ❧ Chapter 4: Challenges lists the challenges including making a decision and communication in a distributed manner. Three related research are discussed and compared with the Dynamic Power Sharing Mechanism. ❧ Chapter 5: System Design shows the whole system structure including software and hardware. In the software part, several main functions which are used to accomplish Power Sharing Functions are introduced. In the hardware part, the hardware design procedure and main components are discussed. ❧ Chapter 6: Dynamic Power Sharing, six Power Sharing scenarios including 1. Offering Power, 2. Bypass Power, 3. Receiving Power Only, 4. Charging the Battery Only, 5. Both Charging the Battery and Receiving Power and 6. Power Sharing Communication Protocol are demonstrated to present how the Self-Reconfigurable Modular Robots share power dynamically. The Power Sharing Communication Protocol was created in order to help each modular robot to negotiate what kind scenario they want to adapt. The Power Sharing Algorithm is also brought out to make the Self-Reconfigurable Modular Robots doing Powering Sharing in a distributed manner. ❧ Chapter 7: Conclusion summarizes the possible power problems which Power Sharing Functions can solve. The future work including large scale, power management, power loss, optimizing Power Sharing in different tasks is discussed.

Linked assets

University of Southern California Dissertations and Theses

Conceptually similar

PDF

Intelligent near-optimal resource allocation and sharing for self-reconfigurable robotic and other networks

PDF

Self-reconfiguration planning for modular robots

PDF

Self-assembly and self-repair by robot swarms

PDF

Self-assembly and self-healing for robotic collectives

PDF

Advanced modulation, detection, and monitoring techniques for optical communication systems

PDF

A meta-interaction model for designing cellular self-organizing systems

PDF

A data driven software platform for process automation, planning and inspection of Contour Crafting large-scale robotic 3D printing system

PDF

Integrated reconfigurable wireless receivers supporting carrier aggregation

PDF

Relative positioning, network formation, and routing in robotic wireless networks

PDF

Managing functional coupling sequences to reduce complexity and increase modularity in conceptual design

PDF

RF and mm-wave blocker-tolerant reconfigurable receiver front-ends

PDF

Coordinating social communication in human-robot task collaborations

PDF

Ubiquitous computing for human activity analysis with applications in personalized healthcare

PDF

Design of low-power and resource-efficient on-chip networks

PDF

Mixed-signal integrated circuits for interference tolerance in wireless receivers and fast frequency hopping

PDF

High-speed and reconfigurable all-optical signal processing for phase and amplitude modulated signals

PDF

Reconfigurable high‐speed optical signal processing and high‐capacity optical transmitter

PDF

Motion coordination for large multi-robot teams in obstacle-rich environments

PDF

High power, highly efficient millimeter-wave switching power amplifiers for watt-level high-speed silicon transmitters

PDF

Sweep-free Brillouin optical time-domain analyzer

Asset Metadata

Creator Chen, Chi-An (author)

Core Title Dynamic power sharing for self-reconfigurable modular robots

School Viterbi School of Engineering

Degree Master of Science

Degree Program Electrical Engineering

Publication Date 05/06/2012

Defense Date 03/09/2012

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag Dynamic,modular robot,OAI-PMH Harvest,Power,power sharing,reconfigurable,robot,self-reconfigurable

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Sawchuk, Alexander A. (Sandy) (committee chair), Shen, Wei-Min (committee chair), Granacki, John (committee member), Khoshnevis, Behrokh (committee member)

Creator Email chianc@usc.edu,jotaro.chen@gmail.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c3-31886

Unique identifier UC11290335

Identifier usctheses-c3-31886 (legacy record id)

Legacy Identifier etd-ChenChiAn-783.pdf

Dmrecord 31886

Document Type Thesis

Rights Chen, Chi-An

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the a...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus MC 2810, 3434 South Grand Avenue, 2nd Floor, Los Angeles, California 90089-2810, USA