ltus - Simon Fraser University

Altus Technologies, c/o School of Engineering Science, Simon Fraser University, Burnaby, B.C. Canada V5A 1S6 Tel: 778.892.3432 E-mail: [email protected]

ltus March 9, 2006 Dr. Andrew Rawicz School of Engineering Science Simon Fraser University Burnaby, BC V5A 1S6 Re: ENSC 440 Design Specification for a High-Rise Window Cleaning System Dear Dr. Rawicz: The attached document, Design Specification for a High-Rise Building Window Cleaning System, describes the design of our proposed device. Our goal is to design and implement an automated window cleaning system for high-rise buildings to eliminate the dangers of having manual labour do the cleaning from a high vertical distance. Our design specification details the design, components, and materials in which our system will be implemented, and the testing requirements to make sure our design meets the functional requirements outlined in our functional requirements document. Our design specification has all the information needed for our proof-of-concept device set for completion in April 2006. Altus Technologies consists of five SFU undergraduate engineering students with expertise and experience in both technical and management backgrounds: Tommy Chiu, Howard Lee, Kelvin Mok, Li Ng, and Hubert Pan. Feel free to contact us by phone at 778.892.3432 or by e-mail at [email protected] if you have questions or concerns. Sincerely,

Kelvin Mok Kelvin Mok CEO Altus Technologies Enclosure: Design Specification for a High-Rise Building Window Cleaning System

Design Specification for a High-Rise Building Window Cleaning System

Project Team: Altus Technologies Kelvin Mok CEO Tommy Chiu COO Li Ng CFO Howard Lee CTO for Hardware Hubert Pan CTO for Software Contact Person: Kelvin Mok [email protected] Submitted to: School of Engineering Science

Simon Fraser University

Dr. Andrew Rawicz CEO and CFO Mr. Steve Whitmore CIO and VP HR Issued date: March 9, 2006 Revision: 1.0

ltus


© 2006, Altus Technologies i

ltus

Revision History

Date Rev. Description Contribution ApprovedMar 9 2006 1.0 All content and formatting

complete Altus T.C.


© 2006, Altus Technologies ii

ltus

Executive Summary

Currently, almost all window cleaning for medium to high-rise buildings are done manually by workers on a cleaning platform or with a simple cable. Employing professional window cleaners to clean high-rise buildings has numerous fundamental flaws. First and foremost is the high risk of injury or death caused by the sheer height, strong winds, and isolation of the work environment. Another issue is the high cost associated with hiring window cleaners due to the salary and high insurance costs, and the expensive equipment. The current demand for high-rise buildings is ever increasing, due to urbanization and a growing population. It is difficult to have affordable window-washing personnel trained to work in an increasingly dangerous environment, and it is also very challenging for architects or developers to design giant structures that takes into account the safety of the window-washing professionals. Altus Technologies seeks to eliminate the disadvantages associated with employing window cleaners by developing an automatic high-rise window cleaning system that would be controlled by an operator at the roof or base of the building. Development of our high-rise window cleaning system will occur in two phases. We will first seek to create a proof-of-concept system with the following key features:

• development costs of less than CDN $2000 • cleans the exterior building surface for a vertical distance of up to 5 m • removes debris such as pieces of grass and leaves stuck on the glass by

natural means, spider webs, wet soil, thick dust, and obvious watermarks The second phase of development will be our design that would go into production, and has the following key features:

• functional on buildings up to 200 m in height • moves the cleaning module horizontally for a length of up to 60 m • removes fingerprints, all watermarks, and bird excrement, in addition to

the cleaning capacity listed for the proof-of-concept device • minimizes the environmental impact caused by the use of water and

detergent through a waste management system The first phase of development is scheduled to be completed in April 2006.


© 2006, Altus Technologies iii

ltus

Table of Contents Revision History................................................................................................................ i

Executive Summary ......................................................................................................... ii

List of Figures ................................................................................................................... v

List of Tables ..................................................................................................................... v

Glossary ............................................................................................................................ vi

1. Introduction ................................................................................................................ 1

2.1. Scope................................................................................................................... 1

2.2. Intended Audience .............................................................................................. 1

2. System Overview ....................................................................................................... 2

3. Control Module .......................................................................................................... 5

3.1. PLC ..................................................................................................................... 5

3.2. User Interface...................................................................................................... 7

3.3. Resource Management and Delivery .................................................................. 8

4. Cleaning Module...................................................................................................... 10

4.1. Liquid Cleaning Agents .................................................................................... 11

4.2. Liquid Containers.............................................................................................. 11

4.3. Cleaning Apparatus........................................................................................... 12

4.4. Cleaning Procedure........................................................................................... 13

4.5. Physical Framework of Cleaning Module ........................................................ 15

5. Mobility Module ...................................................................................................... 18

5.1. Pneumatic and Vacuum Subsystem.................................................................. 18

5.1.1. Vacuum Suction Cups................................................................................... 19

5.1.2. Vacuum Pumps ............................................................................................. 20

5.1.3. Air Compressor............................................................................................. 21

5.1.4. Air and Vacuum Distribution........................................................................ 22

5.2. Down Climb System......................................................................................... 22

5.2.1. Leg Frames.................................................................................................... 25

5.2.2. Level Compensators...................................................................................... 27

5.2.3. Mobility Module Mounting Body................................................................. 28


© 2006, Altus Technologies iv

ltus

5.2.4. Climbing Path and Vacuum Sequence.......................................................... 29

5.3. Rooftop Anchoring and Cabling System .......................................................... 31

5.3.1. Winch and Cabling System........................................................................... 32

5.3.2. Battery Charger............................................................................................. 33

5.3.3. Battery........................................................................................................... 34

5.3.4. Ladder ........................................................................................................... 34

5.3.5. Anchoring and Stability ................................................................................ 34

6. Test Plan .................................................................................................................... 36

6.1. Mobility Module Unit Test Plan ....................................................................... 37

6.1.1. Test Case 1.................................................................................................... 37

6.1.2. Test Case 2.................................................................................................... 37

6.1.3. Test Case 3.................................................................................................... 37

6.1.4. Test Case 4.................................................................................................... 38

6.2. Cleaning Module Unit Test Plan....................................................................... 38

6.2.1. Test Case 5.................................................................................................... 38

6.3. Integration Test Plan ......................................................................................... 39

7. Conclusion ................................................................................................................ 40

8. Sources and References ........................................................................................... 41


© 2006, Altus Technologies v

ltus

List of Figures

Figure 1: System Diagram .................................................................................................. 2 Figure 2: Physical Overview of System.............................................................................. 3 Figure 3: Side View of Cleaning Module and Stepping System ........................................ 4 Figure 4: Front View of Cleaning Module and Stepping System....................................... 4 Figure 5: Example of Ladder Logic Diagram..................................................................... 7 Figure 6: Resource Delivery System Diagram ................................................................... 8 Figure 7: Isometric View of Cleaning Module ................................................................. 10 Figure 8: Handheld Squeegee, Sponge Roller, and Handheld Brush ............................... 12 Figure 9: Sponge Roller and Plastic Tube Configuration................................................. 13 Figure 10: Professional Window Cleaner Process Flowchart........................................... 13 Figure 11: Three-Stage Cleaning Procedure of Cleaning Module.................................... 15 Figure 12: Hanging Ring of Cleaning Module ................................................................. 16 Figure 13: Squeegee Configuration of the Cleaning Module ........................................... 16 Figure 14: Twin Sponge Roller Configuration of the Cleaning Module .......................... 17 Figure 15: System Block Diagram of Mobility Module................................................... 18 Figure 16: Isometric, Front, and Side views of the PIAB FC50P Suction Cup................ 20 Figure 17: Solid Model of the PIAB X10A6-AN Vacuum Pump.................................... 21 Figure 18: Pneumatic Schematic of the Air and Vacuum Distribution System ............... 22 Figure 19: Front, Top, Side, and Isometric Views of the Down Climb System with Vacuum Suction Cups....................................................................................................... 24 Figure 20: Front, Side, Top, and Isometric Views of the Leg Frame of the Down Climb System.............................................................................................................................. 26 Figure 21: Level Compensator for Suction Cup............................................................... 27 Figure 22: Operation of the Level Compensator .............................................................. 28 Figure 23: Design of the Mounting Body ......................................................................... 29 Figure 24: Climbing Path to Produce Stepping Motion for One Leg............................... 30 Figure 25: Diagram of Rooftop Anchoring and Cabling System ..................................... 31 Figure 26: Electrical Design Overview............................................................................. 32 Figure 27: Configuration and Stability Analysis for Rooftop Anchoring System ........... 35 List of Tables

Table 1: Technical Specifications of Omron CPM1A........................................................ 5 Table 2: Input/Output Mapping of Omron CPM1A ........................................................... 6 Table 3: Controls to User.................................................................................................... 8 Table 4: Components of the Cleaning Module ................................................................. 11 Table 5: Technical Specifications of PIAB FC50P Vacuum Suction Cups ..................... 20 Table 6: Technical Specifications of PIAB X10A6-AN Vacuum Pump.......................... 20 Table 7: Technical Specifications of the Power Fist 8058448 Electrical Winch ............. 33


© 2006, Altus Technologies vi

ltus

Glossary

Cleaning Module

Part of the system that does the actual cleaning of the building surface

Control Module

Part of the system that allows for user input and system monitoring

CFM Cubic feet per minute, a standard of airflow measurement

Mobility Module

Part of the system that allows for the cleaning module to move to another surface or area of the building.

PLC Programmable Logic Controller


© 2006, Altus Technologies 1

ltus

1. Introduction

The high-rise window cleaning system is an automated system which cleans the exterior surfaces of buildings without the use of window cleaning professionals directly at the cleaning site. The system consists of three modules: the cleaning module, which cleans and washes the building exterior, the mobility module, which allows for movement of the cleaning module across different surfaces, and the control module, which allows user input to control both the cleaning and mobility modules. The system will be developed in two stages, with the first proof-of-concept stage scheduled for completion by April 2006, and further development in the second stage to create a system for commercialization and mass production.

2.1. Scope

This document describes the design specifications for the high-rise window cleaning system. It fully describes the design considerations and implementation strategies of the proof-of-concept device, with design considerations kept in mind for the second phase of development intended for commercialization. The design and technical information outlined in this document will guide our implementation and testing process of our high-rise window cleaning system. For more information on the physical components, including physical dimensions of all components of the system, SolidWorks files of our design are available from Altus Technologies, and are not included in this document.

2.2. Intended Audience

This document is intended for hardware and software specialists at Altus Technologies to guide the implementation and development phase of the project. Members of the design team will use it to ensure the implementation of our device meets the requirements set out in this document, as well as the functional requirements document, while the project manager will use it as a means to measure project progress and performance. The testing team will use it to verify the functionality of the system, and finally, marketing and sales personnel will use it to develop preliminary promotional material.



ltus

2. System Overview

This section gives a physical overview of our device and an overall functional description for our system. Figure 1 shows the three sub-modules of our system, the mobility module, the cleaning module, and the control module, and how they interact.

Figure 1: System Diagram

As shown in Figure 1, the control unit sends instructions to the mobility unit to control the mechanical movement of the mobility unit, which in turn determines the movement and position of the control unit. The control unit also sends instructions to the cleaning unit to control the cleaning operation. The mobility and cleaning units in turn send sensor data and other types of feedback back to the control unit for processing and operation monitoring. Figure 2 shows a physical overview of our system, showing it being implemented on a building. On top of the building is the first component of the mobility module, which is a cabling and winch system to allow for vertical movement of the cleaning module. Also on top of the building is the control module which controls the overall movement and functionality of the system, as well as providing a user interface for human input and control. The control module is not shown in detail in Figure 2. On the building window itself is the cleaning module as well as the second component of the mobility module – a vacuum suction cup and stepping system that allows for secure vertical movement of the cleaning module.

Cleaning Unit Mobility Unit

Control Unit

movement instructions

cleaning instructions

sensors & feedback

sensors & feedback

movement



ltus

Figure 2: Physical Overview of System

Figure 3 and Figure 4 show the side and front view of the cleaning module and the stepping system. Figure 3 shows two sponge rollers on the left, and a squeegee on the right. The blue and purple bars and the yellow box are components of the stepping system, with the suction cups shown in green. Detailed technical information about all modules of the system will be described in subsequent sections.



ltus

Figure 3: Side View of Cleaning Module and Stepping System

Figure 4: Front View of Cleaning Module and Stepping System



ltus

3. Control Module

3.1. PLC

A PLC is used to control our entire system due to its simplicity, low cost, and its tolerance to electric noise and shocks. Since our system does not require a high level of algorithms and computer control, a PLC is quite suitable for the control implementation of our system, and anything more complex, such as a microcontroller, is actually quite unnecessary for our purposes. A PLC’s robustness and reliability is certainly a bonus for our application. The cleaning module is deployed in an elevated position, and in some cases, more than 250 m off the ground. Therefore, we cannot afford to have the control system fail during its operation. Furthermore, the PLC’s real time performance allows processes executed in a timely fashion. For example, the mobility module should allow the cleaning module to move continuously and smoothly from the top of the building downward, without any pauses or irregularities. One of the biggest advantages in using a PLC is its simplicity in programming through the use of ladder logic. We do not have to perform any heavy coding or sophisticated calculations before arriving at a functional code. Also, the debugging process in ladder logic programming is comparatively easier than many other programming languages. The Omron CPM1A is used for our PLC. Table 1 lists the technical specifications for this PLC.

Number of inputs 12 Number of outputs 8 Power source 120V AC Maximum weight 0.5 kg Basic execution time per instruction 0.72 s to 16.2 s User data memory 1024 words Number of timers/counters 128 Basic execution time per instruction 0.72 s to 16.2 s

Table 1: Technical Specifications of Omron CPM1A The output pins of the Omron CPM1A is used to drive a relay, which in turn supplies power to valves, lights, alarms, actuators and so on.



ltus

The input and output mapping of the Omron CPM1A are specified as follows:

Input Connected to 000.00 Emergency Stop Switch 000.01 Start Switch 000.02 Pause / Stop Switch 000.03 Limit Switch from frame 1 000.04 Limit Switch from frame 2 000.05 Release All Suction Switch 000.06 All Suction On Switch 000.07 Climb Up Switch 000.08 Pressure Sensor from valve 1 000.09 Pressure Sensor from valve 2 000.10 N/A – Expansion Pin 000.11 N/A – Expansion Pin Output Connected to 010.00 Direction Up for the winch 010.01 Direction Down for the winch 010.02 Control signal for valve 1 010.03 Control signal for valve 2 010.04 Control signal for the Cleaning apparatus solenoid(s) 010.05 N/A – Expansion Pin 010.06 N/A – Expansion Pin 010.07 N/A – Expansion Pin

Table 2: Input/Output Mapping of Omron CPM1A As mentioned earlier, ladder logic would be mainly used to program the PLC. Ladder logic is usually used as a hardware representation of an electrical logic circuit. Its main components are coils ( ), contacts -| |-, and outputs –o–. It is best to be described by an example [1]:

| start stop | |--+----| |--+----|\|----( )---| | | | run | | +----| |--+ | | run | | | |-------| |--------------( )---| | run motor |



ltus

Figure 5: Example of Ladder Logic Diagram

Looking at Figure 5, we can see a positive power supply line running through the left hand side of the diagram, and a neutral line running thought the right hand side. The logic always flows from the top left to the bottom right. In this case, start is by default an open switch, and stop is by default a closed switch. Run and motor are the coils in this example. So if the user pushes start, then run would be triggered, which would in turn keep the first line running because it would maintain connected until stop is pressed. The second line would continue to run as long as the coil run is engaged.

3.2. User Interface

To deploy and setup the high-rise window cleaning system, the user must first setup all the hardware of the various modules. Once the system is deployed, and one vertical row of the windows will be cleaned. Afterwards, the user will have to horizontally translate the entire system by the width of the cleaning apparatus and repeat the same procedure. This laborious manual operation is only required in the proof-of-concept device, because of cost and time constraints in implementing the proof-of-concept device; in the commercial version, such manual operation will not be necessary. The following controls are visible to the user: Control Description Start Initiates the automated process of down climbing via the

mobility module. It should be pressed after the mobile unit is in a stable configuration, and ready to clean the windows. This switch can be also used after “pause” or “Emergency Stop” is pressed.

Pause / Stop Temporarily suspends the movement of the mobility module. This option can be used when any minor problem is observed or is about to happen, and where a simple adjustment is necessary to correct the problem.

Emergency Stop Suspends all action of the mobility and cleaning module, with the suction cups activated to adhere to the window. In the case of an emergency, this function would immediately lock the position of the mobile unit for troubleshooting and recovery.

Release All Suction

Used to unlock the cleaning unit from the window for special circumstances.



ltus

All Suction On Used to recover the cleaning module to from special circumstances to the normal operation. It can also be used if the system is deployed mid way along the building instead of starting from the top.

Climb Up Allows the user to retrieve the cleaning module from the bottom of the building after one vertical row of window cleaning has completed.

Table 3: Controls to User

3.3. Resource Management and Delivery

Resources needed by the mobility and cleaning modules are water, electricity, and air. Due to the lightweight requirement of the modules, the sources of these resources will not be mounted onto the modules, but rather on top of the building. Figure 6 shows the system diagram of the resource delivery system. Three sources are shown at the top of the diagram: electricity from an electrical outlet, compressed air from an air compressor, and water from a water tap. In addition to the resources cables, signal cables also connect the limit switches and electric air values of the mobility module to the PLC on the rooftop.

Figure 6: Resource Delivery System Diagram

110V Electricity

Water Tap Air Compressor

Detergent Dilution

Electric Air Valve

PLC

Limit Switches

Control

Electric Power

Vacuum Pumps and Suction Cups

Compressed Air Status Report

Compressed Air

Water Delivery

Cleaning Mobility Module

Rooftop Resources

Cleaning Module



ltus

Water will be carried to the cleaning module via a normal garden hose to provide water for cleaning, while compressed air will be carried to the mobility module through a 1/4” compressed air hose to power the pneumatic system. Electricity will be delivered to the mobility module using extension cables to power the electric air valves, and the signals to control the valves as well as signals to carry status of limit switches on the mobility module will be carried by coaxial cables. The compressor that supplies air to the suction cups is expected to function continuously for the duration of the system’s use, with airflow controlled by air valves.



ltus

4. Cleaning Module

The cleaning module is responsible in cleaning off the dirt and other undesired debris from building windows. This module is mounted on the stepping component of the mobility module as shown in Figure 7 below. Note that the cleaning module only consists of components coloured white in the figure. Liquid containers are not shown in the diagram for clarity.

Figure 7: Isometric View of Cleaning Module

Components of the cleaning module are listed in the following table. Item # Item Name Item Category Item Quantity

1 Hard water Liquid cleaning agents 2.5 Liter 2 Zep Glass Cleaner Liquid cleaning agents 2.5 Liter 3 Plastic container

(3 L capacity) Liquid containers 2

4 Plastic container (1 L capacity)

Liquid containers 1

5 30” plastic squeegee Cleaning apparatus 1 6 30” sponge roller Cleaning apparatus 2 7 30“ floor brush Cleaning apparatus 1 8 30” liquid tube Cleaning apparatus 2 9 Spring Physical framework of

cleaning module 5

10 Cleaning module Physical framework of 1



ltus

frame Cleaning module

Table 4: Components of the Cleaning Module Since it is very difficult to derive a satisfactory cleaning method using a mathematical approach, our overall design for cleaning is mainly derived from the common practice done by professional window cleaners. Therefore, we incorporated similar tools and chemicals used by these professionals, and we also simulate their cleaning process in our physical design.

4.1. Liquid Cleaning Agents

The cleaning agents in the cleaning module consist of hard water and Zep Glass Cleaner, which is used separately in the cleaning procedure. Hard water is preferred over the soft water, because it is relatively inexpensive compared to the soft water, and can be easily obtained in large quantities. Moreover, the Zep Glass Cleaner can be used with hard water without losing its effectiveness. Although there are other chemical agents that are commonly used by professional window cleaners such as Titan GG and Winsol CC detergents, these chemicals are only available from limited distributors, and are very expensive compared to the Zep Glass Cleaner. Zep Glass Cleaner is also safe on all glass surfaces including tinted glass, which satisfies the safety requirement [R30ab] of our functional requirements document [2].

4.2. Liquid Containers

Hard water is delivered from the roof area to both 3.0 L containers through a water hose. The purpose of these two containers is to act as a buffer for the cleaning liquids. Hence, if the water flow from the rooftop is interrupted, the cleaning operation can continue for a controlled time before the operator is able to resume the proper water flow. The cleaning module is able to carry up to 2.5 L of hard water and 2.5 L of diluted Zep Glass Cleaner to be able to wash a window area with 100 m in height and 2 m in width in accordance with requirement [R70ab] [2]. Concentrated Zep Glass Cleaner is stored in a small 1.0 L container on the cleaning module, and constantly feeds to one of the 3.0 L containers during the cleaning operation to produce a diluted cleaning solution.



ltus

Since the liquid in our design is non-corrosive, it is safe to be placed inside plastic containers. The maximum capacity of each large container is 3.0 L, which allows users to refill them easily to the 2.5 L level without spilling.

4.3. Cleaning Apparatus

Three types of cleaning tools are used in our cleaning process: a plastic squeegee, two sponge rollers, and floor brush. Most of these tools on the market are designed for handheld use only, most of which are inexpensive and easily obtainable. Therefore, in our design, we will modify the handheld tools and make it attachable to our cleaning module. Below shows the three cleaning tools.

Handheld squeegee Handheld sponge roller Handheld brush

Figure 8: Handheld Squeegee, Sponge Roller, and Handheld Brush An adjustment of the sponge roller will be made to accommodate the functionality of the cleaning module. A liquid plastic tube is added on top of the roller. Between the surface of the sponge and the plastic tube, there are eight evenly spaced holes on the tube to allow liquid to soak into the sponge as shown in the figure below. This keeps the saturation level constant throughout the sponge.



ltus

Figure 9: Sponge Roller and Plastic Tube Configuration

To avoid instability in the vertical movement of the cleaning module controlled by the mobility module, we limit the width of the cleaning tools to be twice of the width of the mobility module. Therefore, all the handheld tools purchased would have the lengths of 30”, wide enough to clean a large portion of window in one sweep.

4.4. Cleaning Procedure

The cleaning process done by professional cleaners is composed of several stages. Our cleaning module will use a modified version of such a process. The diagram below shows a flowchart that summarizes the whole process:

Figure 10: Professional Window Cleaner Process Flowchart



ltus

The first step involves checking the condition of the window surface. If there is dirt that is insoluble to normal chemical agents or debris that is difficult to pick up using only wet sponges, then the cleaner has to apply a small amount of special corrosive chemical only to those areas to dissolve the unwanted materials. Eventually, it will be possible for the cleaner to use a scrubber to remove the materials. This path is indicated as “Left Branch” in Figure 10, which are rare situations for high-rise windows. After scrubbing is finished, the window is inspected again to make sure no insoluble dirt remains. If no insoluble dirt remains, the cleaner then uses a towel or sponge to remove any remaining debris on the window. In the next stage, the squeegee is used to drive out most of the liquid to ensure a clean window surface. Finally, the cleaner moves on to work on another window. Since the majority of the project costs is from the stepping system, the material used to construct the frame of the cleaning module, the PLC, and the motor for the control module, it will be very difficult to develop a cleaning system that completely simulates the cleaning process of a professional cleaner under a tight budget. Notably, such system would require a sophisticated camera to perform image processing on tracking insoluble material, or sensors that can measure the cleanliness of the surface. Moreover, using a corrosive chemical contradicts to our safety requirement [R67ab] [2]. As mentioned in the functional requirement [R75ab] [2], the design for proof-of-concept system focuses on removing water-soluble dust, and easily removable debris such as spider webs, wet soil, and grass, all of which are very easy to pick up using a wet sponge. Therefore, we do not plan to design or implement any mechanism to remove hard-to-dissolve materials or other debris which require extensive scrubbing. In other words, our cleaning module will only function according to the mandatory “Right Branch” as shown in Figure 10. In our design, we break down the cleaning procedure intro three main stages as shown in Figure 11. In our first stage, we apply water and cleaning solution to the window through a sponge roller. There is no scrubbing motion in the sponge roller, because the main purpose is to spread out the liquid evenly on the window surface. In our second stage, we use another sponge roller, this time only soaked with water, with a floor brush installed on top of the sponge to reduce its rotational speed. The sponge roller would hence turn slower, which results a scrubbing motion to remove any insoluble debris. Another purpose of the floor brush is to capture the insoluble debris from the sponge roller to



ltus

prevent the debris from going back to the window. Finally, the last stage involves with a drying squeegee to remove most of liquid on the window surface.

Figure 11: Three-Stage Cleaning Procedure of Cleaning Module

As illustrated in Figure 2, the cleaning procedure is done from top to bottom as the mobility module travels down the window. Since the mobility module deploys suction cups to stabilize the cleaning module when the system is in use, there is a concern that the suction cups would absorb solid objects or leave marks on the window. Therefore, stage 1 and 2 of Figure 11 are placed before the suction cups to ensure that there are no debris in the suction cups’ path. Although the suction cups may take in liquid agents after the first two stages, the liquid can be easily disposed in the pneumatic system of the stepping mechanism of the mobility module. Finally, the last stage is placed after the suction cups, to remove any marks that may result from the suction cups.

4.5. Physical Framework of Cleaning Module

As shown in Figure 7, the main body of the cleaning module is placed on top of the mobility module. In addition, the cleaning module frame has a vertical length of 52.65” and is made out of aluminum, a material that provides a light weight and strength needed for our system. On the front-end of the main body, there is a hanging ring that is responsible for connecting the cleaning module and the stepping system of the mobility module with the cable extending from the rooftop. The location of the hanging ring is shown in the following figure.



ltus

Figure 12: Hanging Ring of Cleaning Module Three arms extend from the main body to hold the cleaning tools. The squeegee is mounted by a single inclined arm, and a spring is added between the inclined arm and the main body to sustain a 60° angle. The figure below shows a diagram of the squeegee configuration on the cleaning module. Note that the hanging ring is omitted in the figure to show the squeegee.

Figure 13: Squeegee Configuration of the Cleaning Module Sponge rollers are found in the lower end of the cleaning module, and is attached to the main body by a pair of extending arms that are fixed at 60° angles. Each arm is spring loaded, to allow the cleaning tools to stay firmly on the window. The spring-loaded joints also allow the cleaning tools to pass over obstacles such as window frames. The figure below shows the configuration of the twin sponge rollers. Note that the liquid tubes are placed above the sponge roller to ensure the liquid travels to all parts of the sponge. The liquid plastic containers are not shown in the figure for clarity. They are mounted on one end of the liquid tube, with the other end of the tube is closed.



ltus

Figure 14: Twin Sponge Roller Configuration of the Cleaning Module



ltus

5. Mobility Module

The mobility module contains all parts of the system that moves the cleaning module. There are three major subsystems to the mobility module: 1. The pneumatic and vacuum subsystem 2. The down climb stepping subsystem 3. Then rooftop anchoring and cabling subsystem Subsystems 1 and 2 mentioned are directly attached to the cleaning module to allow anchoring of the cleaning module to the building, while subsystem 3 provides mobility or a controlled drop to the cleaning module via a cabling system. Figure 15 shows how the subsystems relate to each other and the general system diagram of the mobility module.

Figure 15: System Block Diagram of Mobility Module

5.1. Pneumatic and Vacuum Subsystem

One problem with window cleaning at high elevation from the ground is high-speed winds causing instability to the cleaning module. In order to provide stability to our cleaning module under windy conditions, we anchor the cleaning

Motor and Cabling

Mounting Body of Mobility Module

Down Climb System

Pneumatics and Vacuum

Cleaning Module

vertical movement

stepping motion

stability and horizontal force

attachment



ltus

module to the window using vacuum suction cups that are controlled by a pneumatic system. The system consists of vacuum suction cups, vacuum pumps, an air compressor, air control valves, and an air distribution system.

5.1.1. Vacuum Suction Cups

Our criteria for selection vacuum suction cups are based on its perpendicular and parallel (shear) force ratings, while minimizing cost. We also restricted the choice of suction cups to ones that do not leave marks, because the majority of the cleaning is done before the cups. If the cups were to leave marks, there will be a high probability that our cleaning module will not be able to clean those marks. These suction cups are mounted on two leg frames, with four cups on each leg, for a total of eight cups for our system. With four cups on each leg, the design of the leg frame will be such that at any given time, there will be at least three suction cups attached to the widow per leg. For example, when the stepping system is used to move the cleaning module downwards, a window frame might block one suction cup, but our redundancy design in suction cups per leg frame will allow it to still firmly adhere to the window surface. Leg frames will be discussed in more detail in Section 5.2.1. In the design of the mobility module, the supporting cable attached to the motor located at the rooftop will bear the main weight of the cleaning module and the down climb stepping system. Thus, the suction cups only need to bear the weight of the leg frames, as well as exert enough force onto the window to achieve the pressure for cleaning purposes. From experiment trials of cleaning a scale, we realized that the cleaning module is required to exert a force of 10 lbs onto the window. In other words, three suction cups must be able to provide at least 10 lbs of force onto the window. As well, each leg frame is estimated to be approximately 5 lbs. Thus, three suction cups must sustain at least 5 lbs of shear load. PIAB FC50P vacuum suction cups are used for our system. Technical specifications are given in the table below. Note that 6“hg is a vacuum level that our vacuum pump can easily achieve.

Material polyurethane Volume inside cup 0.61”3 Perpendicular force sustained per cup 6.29 lbs



ltus

(under 6“hg of vacuum pressure) Parallel force sustained per cup (under 6“hg of vacuum pressure)

11.7 lbs

Approximate safety factor, assuming only 3 suction cups adhered to window surface

7

Table 5: Technical Specifications of PIAB FC50P Vacuum Suction Cups The polyurethane composition of the FC50P suction cups ensures that does not leave marks on the window. Isometric, front, and side views of the PIAB FC50P suction cup are shown in the figure below.

Figure 16: Isometric, Front, and Side views of the PIAB FC50P Suction Cup

5.1.2. Vacuum Pumps

In order for the suction cups to work, a vacuum must be created. Our design uses PIAB X10A6-AN vacuum pumps to create the vacuum. These vacuum pumps create a vacuum using compressed air, and are fully pneumatic, meaning that we do not need to deal with any electronics to control the pumps, and the system will only use one compressor to power all vacuum pumps. One vacuum pump will be used to power a set of four pumps on each leg, instead of using one pump for each suction cup. The technical specifications of the vacuum pump are shown in the table below.

Evacuation time for a vacuum pressure of 6“hg 13.3s/cubic foot Maximum vacuum level 27.9“hg

Table 6: Technical Specifications of PIAB X10A6-AN Vacuum Pump



ltus

These specifications fully meet our needs, and we plan to use a vacuum level of 6“hg for the cups. Figure 17 shows a solid model of the PIAB X10A6-AN vacuum pump.

Figure 17: Solid Model of the PIAB X10A6-AN Vacuum Pump

We chose to use only two pumps because of the high 1.67 CFM air consumption of the vacuum pumps. Furthermore, the rating on the pumps and from our own trials show that one pump is able to create enough vacuum of all four suction cups. If one of the cups is not sealed, the vacuum pump is still able to maintain enough vacuum for the other three cups to adhere to the window surface and provide enough force for cleaning.

5.1.3. Air Compressor

The choice of compressor has one main constraint, which is the airflow it is able to provide at the rated optimum pressure of 72 PSI for the PIAB X10A6-AN vacuum pumps. Experiments with the PIAB vacuum pumps so far are done using a 1 HP air compressor that is able to provide 4 CFM at 60 PSI. Our trials show that such a compressor will be able to supply sufficient air to two vacuum pumps. Due to the heavy weight of the compressor (the one we used so far weighs approximately 60 lbs), we do not want place it onto the mobility module. Thus, the air compressor will be placed at the top of the building, and compressed air will be routed using an air hose.



ltus

5.1.4. Air and Vacuum Distribution

Figure 18 shows the pneumatic schematic diagram of the air and vacuum distribution system. One compressor supplies compressed air to two vacuum pumps. Each vacuum pump uses the compressed air as input, and provides vacuum as its output. One pump will provide a vacuum for four suction cups on one leg.

Figure 18: Pneumatic Schematic of the Air and Vacuum Distribution System

Electric valves are placed at the input of the two vacuum pumps to cut off the compressed air at timed intervals to result in deactivation of the vacuum pump and cups. The vacuum pumps and cups will deactivate because the pumps require continuous flow of compressed air to create and maintain a vacuum. When no compressed air enters the pumps, they lose vacuum rapidly and will result in deactivation of the suction cups. The purpose of deactivating the pump and cups is to allow the specific leg to release itself from the window surface and step down in order to achieve the down climb motion. Details of the down climb system will be discussed in more detail in the next section.

5.2. Down Climb System

With the pneumatic and vacuum subsystem, the cleaning module can be stable and have enough force on the window surface to perform the cleaning function.

Compressor

Pressure Tank Pressure Gauge

NO Air Valve, Closed when Coil Energized

Exhaust

Vacuum Pump

Vacuum Suction Cup



ltus

However, to fully clean windows, the cleaning module must be able to move vertically and at the same time continually apply pressure against the windows for proper application of the cleaning tools. In addition, the mobility and cleaning modules must always anchor to the building to maintain stability under windy conditions. To achieve vertical movement without releasing the cleaning module from the window, we design an innovative down climb stepping system that utilizes gravity to power the stepping motion. Such a system will be discussed in more detail in later subsections. Such a design allows for low complexity, reduced use of actuators, and low power consumption. Figure 19 shows the various views of the down climb system with two leg frames, one leg mounting body, and eight level compensators attached to eight suction cups. The rectangular box at the bottom of the system serves as storage space for materials/subsystems needed by the cleaning module.



ltus

Figure 19: Front, Top, Side, and Isometric Views of the Down Climb System with

Vacuum Suction Cups



ltus

5.2.1. Leg Frames

The leg frame of the down climb system is shown in the figure below. It is made out of 1” hollow aluminum square beams with 1/8” thick walls. Aluminum allows the mobility module to be as lightweight as possible. Four suction cups are mounted on each frame.



ltus

Figure 20: Front, Side, Top, and Isometric Views of the Leg Frame of the Down

Climb System

Two of these leg frames will be used for the system, with each leg estimated to weigh approximately 5 lbs. The slanted design the frame as shown in Figure 20 means no two cups are horizontally in line with one another, which ensures if a cup is obstructed by a window frame, the other three will still touch the window. A minimum of three cups is needed to provide a rigid triangular formation for



ltus

adequate stability and force to the window surface. In other words, the dimensions of the leg frame are designed such that no more than one cup can be obstructed by the window frame at any time.

5.2.2. Level Compensators

When a suction cup becomes obstructed by a window frame, the other three cups must touch the window to provide stability and force. If all cups were mounted on rigid metal rods, the obstruction would cause the whole system to leave a gap between the window and the remaining cups. To prevent this problem, a level compensator, like the one shown in the figure below is placed at the cup mounting.

Figure 21: Level Compensator for Suction Cup

The spring used for the level compensator will have a very low spring constant and enough compression to function with normal window frames (approximately 0.7” for our planned demo site). A low spring constant is needed because we want to make sure that the spring does not push the system away from the window, but that it simply allows the obstructed suction cup to retract. The figure below shows the operation of the level compensator when one cup is obstructed.



ltus

Figure 22: Operation of the Level Compensator

5.2.3. Mobility Module Mounting Body

The mounting body holds the two legs together, connects the cabling system from the rooftop, and serves as the attachment point between the cleaning module and the mobility module. In other words, the mounting body is the main body of the mobility module, and holds everything together. Our design uses wood panels to construct the mounting body, and 1/4” hollow aluminum square beams with 1/16” thick walls to reinforce the body. Wood is used because of the climbing path for the down climb system to work requires trial and error, since we are unable to accurately simulate it using a computer program. Furthermore, we do not have the tools or the expertise to create precise paths in metal, but we do have woodworking experiences and tools. The mounting body will be built using metal for the second phase of development. However, for our proof-of-concept device, wood is the material of choice. Figure 23 shows the design of the mounting body.

No Obstruction Obstruction

Window Frame

Vacuum Suction Cup

Level Compensator at Work



ltus

Figure 23: Design of the Mounting Body

5.2.4. Climbing Path and Vacuum Sequence

The major innovation of the climbing system lies in the climbing path combined with the vacuum sequence to produce a gravity powered, down climb system. As shown in Figure 20, each leg frame contains four knobs on the vertical beam. These four knobs will be attached to small wheels which will fit into the paths in the mounting body, as shown in Figure 23. The way the two legs step is due to the restricted climbing path in the mounting body and gravity. Since the legs are mounted into the climbing paths, with

Climbing Paths



ltus

wheels in the grooves, gravity will always want to pull the legs down. Yet, when suction is turned on, the leg remains in place, and as the cable lowers the mounting body, the attachment wheel of a leg will tend to travel up the groove. Figure 24 shows the functions just described to achieve the down climb motion. The travel path is designed such that the leg will move outward, away from the window when it is dropping down, and it will remain close to the window when it is traveling up the path by remaining in same position while the mounting body is dropping.

Figure 24: Climbing Path to Produce Stepping Motion for One Leg

With gravity acting as the main actuator for the down climb system, it will now be much simpler compared to other implementations which may require actual physical actuators. However, in addition to the travel path, the moment that vacuum should be turned on and off at each leg must be carefully calculated and tested. Particularly, the vacuum for cups on one leg will be turned on when it has reached the bottom of the travel path. Once the leg has reached the top of the travel path, the vacuum will immediately be turned off. This vacuum sequence is

Window

Cycle repeats

Suction on; leg remain at same place; body dropping down; leg follows path

Suction now off; leg drops much faster than body; leg drops off following path that make suctions cups move a little away from window; body dropping down at same rate as before

Leg reached top of path; body continues to drop; suction will turn off

Leg at bottom of path pushing towards window; body dropping down



ltus

programmed through the use of limit switches on the legs and using the PLC to control the electric air values as mentioned in Section 5.1.4.

5.3. Rooftop Anchoring and Cabling System

The vertical movement of the unit is controlled by a cable tied to a winch at the rooftop. As suggested in requirement [R11ab] in the functional specifications [2], the weight of the cleaning module and down climb mobility subsystem is a maximum of 40 kg. The winch is suspended from the edge of the roof by a ladder. The other end of the ladder is anchored using a counterweight composed of bricks. To ensure the system is completely secured on the rooftop, additional cables are used to tie the ladder to anchoring points on the rooftop. The design is summarized in Figure 25.

Figure 25: Diagram of Rooftop Anchoring and Cabling System

The electrical component of the system involves the use of a batter charger, a battery, and a winch, shown in Figure 26. The 12V battery charger serves as a transformer to step down the power source from 120V AC to 12V DC. It is also



ltus

capable of supplying the average current required for the winch. A battery is connected in parallel with the winch and the battery charger, and serves two purposes:

1. It acts as a reservoir of energy, and supplies all the current necessary during peak load, as demanded by the winch. This current can exceed the energy supplies from the batter charger, but not for a prolonged period.

2. It stabilizes the noisy DC output from the battery charger. The winch

would require a constant DC input at its rated voltage.

Figure 26: Electrical Design Overview

5.3.1. Winch and Cabling System

The winch and cabling must be able to support a load of up to 40 kg (97 lb), at a down climb speed of no faster than 0.1 m/s. It should also be capable of bidirectional movement to allow the user bring the cleaning module back to the top. In addition, the mechanism has to stop the cleaning module from falling when the winch stops functioning. An ideal off-the-shelf component that fits our requirement is an electrical winch.

12V Charger

+ -

120 VAC 12VDC Battery Charger

12VDC Lead-acid Battery

2000 lb Winch

Electrical Input

Mechanical Output



ltus

The Power Fist electrical winch with AP part number 8058448 is quite suitable for our system, and its technical specifications are shown in the table below.

Maximum load capacity 2000 lbs Safety factor for a 40 lbs load 22 Line speed at no load condition 0.0508 m/s Motor 0.85 HP Gear ratio 153:1 Cable 49’ X 5/12 “ Other features 10’ handheld remote Gear ratio 153:1

Table 7: Technical Specifications of the Power Fist 8058448 Electrical Winch

For the proof-of-concept device, it will only need to function for three stories of windows. The specifications of the electrical winch are more than enough for our purposes.

5.3.2. Battery Charger

To find the battery charger requirements, we perform a power analysis. At 2000 lbs maximum load condition, the winch motor consumes 0.85 HP, equivalent to 634 W. Assuming a constant voltage of 12 V, the peak current required is 53 A. However, this is not our operating current if the load is less than 88 lbs. Using a linear relationship between force and current:

Fneeded / Fpeak = Ineeded / Ipeak

Ipeak is found to be 2.33 A. Thus, the charger has to sustain an output current of 2.33 A at 12V. Since we have a battery to act as a voltage regulator, the charger does not need to output a clean DC voltage. The MotoMaster battery charger chosen for our system is capable of delivering a maximum of 55 A at 12V. The high current is normally needed to initiate the starter or to charge an empty battery. The charger automatically shuts off when the battery reaches its capacity at 12V. Thus, the winch is powered by the battery until the voltage across the terminal drops below the threshold of the charger. The battery charger then switches on and delivers power to both the battery and the winch.



ltus

5.3.3. Battery

The operating voltage of the system is determined to be 12 V DC, and the battery serves as a stabilizer for this voltage. To provide a current of 20 A-hrs at 12 V, we use a battery with a lead-acid core, instead of gel cells such as Ni-MH and Ni-Cd. Lead-acid batteries tend to have a high power-to-weight ratio which is desired in our system. In addition, lead-acid batteries are inexpensive and provide a large surge current. Our design uses a sealed battery to prevent acid from leaking out and impurities from getting into the chemical body.

5.3.4. Ladder

To create an extended hanging mechanism from the side of the rooftop, a ladder is used for its relatively rigid structure and light weight. We use an off-the-shelf 16’ aluminum extension ladder with a weight of 16.5 kg (36.3 lbs), with a maximum load capacity of 200 lbs. Assuming the extension ladder is used for climbing up a wall, forming a 45° angle with horizontal, if a 200 lbs force is directed downward in the middle of the ladder, this would imply that the normal force supplied from the ground to be at least 200 lbs, in addition to the weight of the ladder. Since the ladder is at an angle of 45°, the force splits into two components, with one parallel to the length, and the other normal to the climbing surface. Thus, our ladder can handle at least a torsion load of 100 lbs for our purposes. With the weight of the winch is plus the weight of the system being less than 100 lbs, our ladder would be safe enough to be used for our system.

5.3.5. Anchoring and Stability

The anchoring system at the rooftop must be securely firmly and balanced to prevent instability or the ladder from dropping. Figure 27 describes the configuration and stability analysis for the anchoring system.



ltus

Figure 27: Configuration and Stability Analysis for Rooftop Anchoring System

With the ladder with a weight of 36.3 lbs, the maximum weight of the winch being 15.9 lbs and weight of the mobile unit well under 60 lbs, Figure 27 shows that the anchoring the system will be stable, with a safety factor of 45. The counterweight at the end of the ladder can be further increased in weight to create additional safety for the system.

7.35” 180”

192”

96” FW

FM

FL FB

Winch

Mobile Unit

ladder

pivot

brick

Building



ltus

6. Test Plan

The modular approach to our system allows each component to be tested and verified individually before overall system testing and integration. As mentioned previously in our system overview section, we have divided our high-rise building window cleaning system into three modules - the mobility module, the cleaning module, and the control module. We will be verifying the functionality and performance of several critical items within each module, and also for the complete module. Our testing team will be focus testing on the complete modules that are mainly composed of mechanical parts, namely, the mobility and cleaning modules. This is the most critical area of our whole system, and an area in which most of the knowledge and experience of the team must be focused on for the project to be successful. The critical items for testing are outlined below: Control Module Critical items: PLC ladder logic program, motor, and user interface. Our testing team will perform the following verifications:

• Verify the designed behavior of PLC ladder logic program by simulating the program on an offline simulator.

• Verify the motor rotation speed under a range of load weights. • Verify that all the buttons of the user interface are responsive.

Mobility Module Critical Items: air compressor, vacuum pump, and suction cup. Our testing team will perform the following verifications:

• Verify that the air compressor is maintaining a constant pressure during operation.

• Verify that the vacuum pump sustains a vacuum using the air compressor. • Verify that the suction cups can hold the designated maximum weight

when coupled with the vacuum pump and air compressor. Cleaning Module Critical Items: squeegee and sponge roller. Our testing team will perform the following verifications:



ltus

• Verify that the squeegee is able to drive most of water from a wet surface. • Verify that the sponge roller can soak enough water and evenly spread

water on a surface.

6.1. Mobility Module Unit Test Plan

6.1.1. Test Case 1

Requirement: Mobility module must stay firmly on a dry wall. Procedure: Mount the mobility module on a dry and flat vertical window. Set the module to park mode. Mark the initial position of the module on the window. Exert reasonable pull and push force on the module. Expected Result: Module stays on the surface, and does not leave the marked position.

6.1.2. Test Case 2

Requirement: Mobility module must stay firmly on a wet wall. Procedure: Simulate the cleaning environment by spreading hard water and Windex auto glass cleaner over a flat vertical window. Distribute the liquid evenly on the surface using a sponge roller. Mount the mobility module on the window surface. Set the module to park mode. Mark the initial position of the module on the window. Exert reasonable pull and push force on the module. Expected Result: Module stays on the surface, and does not leave the marked position.

6.1.3. Test Case 3

Requirement: Mobility module moves vertically for a maximum distance of 5 m. Procedure:



ltus

Mount the mobility module on a dry and flat vertical window wall. Make sure that there are physical obstacles on the wall such as window frames. Initially set the module to park mode. Mark the initial position of the module on the window. Mark the final position by locating a distance of 5 meters directly below the initial position. Set the module to moving-down mode. Stop the module when it reaches the final position. Set the module to park mode again, and then switch it to moving-up mode. Stop the module when it goes back to the initial position. Expected Result: Module travels to final position, and then goes back up to initial position without any trouble.

6.1.4. Test Case 4

Requirement: The emergency stop function stops the all movement of the system. Procedure: Mount the mobility module on a dry and flat vertical window. Mark a position by locating a distance of 2 meters directly below the initial position. Initially set the module to park mode. Set the module to moving-down mode. Make sure the mobility module is moving at constant speed. Once reach the final position, hit the emergency stop button. Expected Result: Module stops firmly at the final position.

6.2. Cleaning Module Unit Test Plan

6.2.1. Test Case 5

Requirement: Cleaning module performs effective cleaning on a dirty window. Procedure: Prepare a clean and dry flat window. Spread dust obtained from a vacuum cleaner and/or chalk from a chalkboard on the window. Make sure the window is vertically mounted. Hold the cleaning module at its operating distance from the window. Start the cleaning process from the top, and then move the cleaning module slowly to the bottom.



ltus

Expected Result: The dust is gone from the window surface, and the window appears to be clean and dry as originally prepared.

6.3. Integration Test Plan

The final integration for the proof-of-concept device occurs when the control module is complete and the mobility and cleaning modules have passed the unit testing process. Instead of performing the test in a simulated environment, integration testing will be done on a real building. We have surveyed the buildings at the SFU Burnaby campus and have found two optimum locations for performing our integration testing. Currently, we are in the process of working with SFU Facilities Management to receive safety training and authorization to use the test sites. The goal for integration testing is to ensure all the modules work properly and is synchronized with each other in a real environment rather than in a controlled surrounding. In addition, integrating testing shows that the system is able to demonstrate the main functionalities outlined in the functional specification document [2].



ltus

7. Conclusion

Altus Technologies is determined to tackle the problems inherent in today’s high-rise window cleaning industry with our high-rise window cleaning system. The design specifications set out for our system is innovative, cost-efficient, and user-friendly. This is necessary, since only a top-notch system will be able to satisfy the current high standards in the high-rise window cleaning industry. We are confident that our proof-of-concept device will demonstrate the feasibility of our proposed window cleaning system. In April 2006, our first stage of development, the design and creation of the proof-of-concept system will be complete, and a demonstration of our device will be performed to show the applicability and effectiveness of our high-rise window cleaning system.



ltus

8. Sources and References

[1] Wikipedia, Ladder Logic, 2006. [online]. Available: http://en.wikipedia.org/wiki/Ladder_logic [Accessed: March 1, 2006]

[2] Altus Functional Requirements for a High-Rise Window Cleaning System, 2006. [online]. Available: http://www.ensc.sfu.ca/~whitmore/courses/ensc305/projects/current/altfunc.pdf [Accessed: March 1, 2006]

[3] Suction Cups FC-P FC50P, 2006. [online]. Available: http://www.piab.com/Templates/WebBase/Datasheet.aspx?id=10134 [Accessed: March 3, 2006]

[4] Vacuum Pumps Mini X10L, 2006. [online]. Available: http://www.piab.com/Templates/WebBase/Datasheet.aspx?id=10250 [Accessed: March 3, 2006]

[5] Introduction to Pneumatics and Pneumatic Circuit Problems for FPEF Trainer, 2006. [online]. Available: http://www.clippard.com/downloads/general/PDF_Documents/Intro_to_Pneumatics.pdf [Accessed: March 3, 2006]

[6] PLC Programming Notations, 2005. P. Leung. Simon Fraser University

[7] PLC Operations and characteristics, 2005. P. Leung. Simon Fraser University

[8] PLCapps_04.ppt Why use PLC’s ? , 2005. P. Leung. Simon Fraser University

[9] The Unique World of Princess Auto Spring & Summer 2006 Catalogue, 2006. Princess Auto, Coquitlam, BC.

[10] Electric Winch, 2006. [online]. Available: http://hotproducts.alibaba.com/manufacturers-exporters/Electric_Winch.html [Accessed: March 5, 2006]

[11] Battery (electricity), 2006. [online]. Available: http://en.wikipedia.org/wiki/Battery_(electricity) [Accessed: March 5, 2006]

[12] Micro Programmable Controller CPM1A, 2006. [online]. Available: http://oeiwcsnts1.omron.com/pdfcatal.nsf/PDFLookupByUniqueID/ E28AFDD58D0167FD86256E63005D8599/$File/D11CPM1A0304.pdf?OpenElement [Accessed: March 5, 2006]

Date post:	08-Apr-2022
Category:	Documents
Upload:	others
View:	5 times
Download:	0 times