project proposal and feasibility study (ppfs)

Team Four: Hydraulic Hybrid

Project Proposal and Feasibility Study

12/10/2010

Team 4: Hydraulic Hybrid Senior Design Project

Tim Bangma | Jon Mulder | Zach Talen | Jay Prins | Liz Kladder

CALVIN COLLEGE ENGINEERING

PROJECT PROPOSAL AND FEASIBILITY STUDY



Abstract:

This report describes the feasibility of the Team Hydraulic Hybrid’s senior design project. This report outlines and presents the feasibility of the project by exploring market research, design, evaluation procedures, and a financial analysis for a retro-fit series hydraulic system to install in a gasoline engine driven vehicle. The goal of this project is to increase energy efficiency of the vehicle by 40 % with the hydraulic system. Currently, several companies are developing similar parallel systems for delivery truck applications; however, none of these systems use only hydraulics to power the wheels in all situations. The prototype outlined in this report is a small golf cart equipped with a gasoline engine and a series hydraulic system, consisting of a hydraulic pump, high pressure accumulator, and a hydraulic drive motor. The analysis and calculations performed in this report concluded the project is feasible and will be implemented in the spring. The prototype vehicle will be constructed and tested in time for the Senior Design Banquet on May 7, 2011.



Table of Contents

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

1.1 Project .............................................................................................................................. 1

1.2 Team Synopsis .................................................................................................................. 1

2. Market Research .................................................................................................................. 3

3. Design Norms ....................................................................................................................... 4

3.1 Stewardship ...................................................................................................................... 4

3.2 Trust ................................................................................................................................. 4

3.3 Transparency .................................................................................................................... 4

4. Project Management ........................................................................................................... 5

5. Overall System ..................................................................................................................... 6

5.1 Requirements ................................................................................................................... 6

5.2 Design Process .................................................................................................................. 6

5.3 Proposed Design ............................................................................................................... 6

5.4 Feasibility .......................................................................................................................... 7

5.5 Evaluation Process ........................................................................................................... 7

6. Vehicle Chassis ..................................................................................................................... 9

6.1 Requirements ................................................................................................................... 9

6.1.1 Strength..................................................................................................................... 9

6.1.2 Size ............................................................................................................................ 9

6.2 Design Procedure ............................................................................................................. 9

6.2.1 Design Alternatives ................................................................................................... 9

6.3 Proposed Design ............................................................................................................. 10

6.4 Financials ........................................................................................................................ 10

7. Hydraulic System................................................................................................................ 11

7.1 Components ................................................................................................................... 11

7.2 Requirements ................................................................................................................. 11

7.3 Gearing ........................................................................................................................... 11

7.4 Design Procedure ........................................................................................................... 11



7.4.1 EES Calculations ...................................................................................................... 12

7.4.2 Simulink Calculations .............................................................................................. 13

7.4.3 Design Alternatives ................................................................................................. 16

7.5 Proposed Design ............................................................................................................. 16

7.6 Feasibility ........................................................................................................................ 16

8. Primary Power Source ....................................................................................................... 17

8.1 Requirements ................................................................................................................. 17

8.1.1 Power, Torque, and Speed ...................................................................................... 17

8.1.2 Engine Dimensions .................................................................................................. 17


8.2.1 Calculations ............................................................................................................. 18


8.3 Proposed Design ............................................................................................................. 18

8.4 Financials ........................................................................................................................ 18

9. Controls System ................................................................................................................. 19

9.1 Requirements ................................................................................................................. 19


9.2.1 Calculations ............................................................................................................. 19


9.3 Proposed Design ............................................................................................................. 21

10. Drivers Comfort and Safety................................................................................................ 22

10.1 Comfort ....................................................................................................................... 22

10.2 Safety .......................................................................................................................... 22

11. Business Financials ............................................................................................................. 23

11.1 Prototype Cost ............................................................................................................ 23

11.2 Retrofit System Cost and Selling Price ........................................................................ 23



Table of Figures

Figure 1: Series Hydraulic Hybrid System ....................................................................................... 7Figure 2: Diagram of Baseline Drive System ................................................................................... 8Figure 3: Diagram of Hydraulic Drive System ................................................................................. 8Figure 4: Varying Accumulator Pressure with Velocity of the Vehicle ......................................... 12Figure 5: Graph of Accumulator Pressure (psi) vs. time (s) .......................................................... 13Figure 6: Vehicle Velocity vs. Time ............................................................................................... 14Figure 7: Close-Up of Accumulator Pressure Graph ..................................................................... 15Figure 8: Close-Up of Vehicle Velocity Graph ............................................................................... 15Figure 9: Controlled Accumulator Pressure .................................................................................. 20

Team Four: Hydraulic Hybrid 1


1. Introduction Calvin College is a four-year, liberal arts college in Grand Rapids, Michigan that offers a variety of undergraduate degrees. The Calvin engineering program is accredited by the Accreditation Board of Engineering and Technology (ABET) to provide Bachelor of Science in Engineering degrees in Chemical, Civil & Environmental, Electrical & Computer, and Mechanical concentrations. As a part of the engineering program, seniors partake in a design project that is part of a two semester long capstone course, ENGR 339 and 340. The main objectives of the first semester of the course are identifying a project for the team and performing a feasibility study of the project. In the second semester, teams focus on designing and implementing the project. The following report outlines and presents the feasibility of the hydraulic hybrid project by exploring market research, design, evaluation procedures, and a financial analysis.

1.1 Project The goal of this project is to validate the claim that a gas-hydraulic hybrid drive system with regenerative braking can significantly increase the energy efficiency. The project aims to increase the overall vehicle fuel efficiency by 40% while maintaining normal performance. The ideal vehicle for this system’s implementation is one operating in frequent stop and start circumstances, such as postal trucks, delivery trucks or city buses. Frequent stopping and acceleration is an inefficient use of energy, since energy is wasted when braking. For this project, however, a hydraulic system will be retrofitted to a golf cart due to time and budget constraints.

1.2 Team Synopsis Tim Bangma is a senior engineering student with a mechanical concentration at Calvin College. He grew up in Whitinsville, Massachusetts, attended Whitinsville Christian School, and spent his summers working at a local fruit and vegetable farm stand. Ever since he was young, he had a passion for designing, building, and working on mechanical things from Legos, to dirt bikes, to cars. Tim has interned part-time with Innotec Group in Zeeland, Michigan, and full-time during the summer of 2010 as a machine designer with Extol Inc., also in Zeeland, Michigan. Tim is still currently looking for a full-time job after graduation in May of 2011.

Liz Kladder is a senior engineering student with a mechanical concentration who is also receiving a minor in business. Originally from Holland, Michigan, she began her college career at Willamette University in Salem, Oregon. She now lives in Grand Rapids with her husband, Jon, and her dog, Bosun. She loves to be outdoors, whether she is hiking, biking, snowboarding, or sailing on beautiful Lake Michigan. During her time at Calvin, Liz has had the valuable opportunities to work at both Profile Industrial Packaging in Wyoming, Michigan and at Gentex Corporation in Zeeland, Michigan. She is looking into post-graduation, full-time employment opportunities where she can pursue a future in mechanical engineering.



Jon Mulder is a senior engineering student with a mechanical concentration at Calvin College. He grew up in Jenison, Michigan and attended Jenison Christian School and Unity Christian High School. He loves to spend time with friends and family and enjoys golfing, singing, and watching the Detroit Tigers. Jon has gained engineering knowledge and experience while working as a Quality Intern at Stanley InnerSpace in Kentwood, Michigan. Upon obtaining his degree, Jon plans to join the work force and is open to any and (almost) every opportunity.

Jay Prins is a senior engineering student with a mechanical concentration at Calvin College. Originally from Loveland, Colorado, he enjoys running in road races, snowboarding, and fishing in his spare time. Jay spent the summer of 2010 working at General Motors Component Holdings in Grand Rapids, Michigan as a test engineer intern. After graduation in May 2011, Jay is seeking full-time employment where he can use his engineering skills and innovative ideas to benefit the company.

Zach Talen was born in Bakersfield, California, but moved Grand Rapids, Michigan at the age of five. He is now a senior at Calvin College majoring in engineering with a mechanical concentration. He enjoys living a life of adventure, which includes spending time outdoors and on the water. Zach enjoys sailing, water skiing and snowboarding. He has worked around engineers since he was in high school, but recently acquired an internship at Gentex Corporation working within the prototype and applied materials areas. He works with engineers who are responsible for being the last line of defense in problem solving as well doing continual improvement projects on the machines. Post graduation, Zach will be leaving for a five month adventure to sail to the Caribbean, from Michigan. Once he returns he will be getting married and looking for a job that utilizes his degree and his passions within the engineering field.



2. Market Research While hybrid vehicles are becoming more common every day, hydraulic hybrids are less well known than electric hybrids. The major advantage of a hydraulic hybrid system over an electrical hybrid system is its ability to function without a battery. Batteries can be difficult to dispose of properly and expensive to replace. Hydraulic hybrids are more efficient than electric hybrids because energy is converted from potential energy directly into mechanical energy. Electric hybrids require chemical energy to be converted into electrical energy which is then finally transformed into mechanical energy. Each energy conversion decreases the amount of energy that is available due to inefficiency.1

The two major market leaders of hydraulic hybrid systems are Parker Hannifin Corporation and Eaton Corporation. In 2005, the Environmental Protection Agency partnered with both the United States Parcel Service (USPS) and Eaton Corporation to create a number of series hydraulic hybrid powered trucks for the United Postal Service (UPS).

Although hydraulic hybrids are more efficient than an electric hybrid, a battery is necessary to include for electrical components such as air conditioning, radios, and clocks.

2

The hydraulic hybrid system is able to save a significant amount of energy through regenerative braking because UPS trucks often make frequent stops and starts making deliveries in urban traffic.

1 How Hydraulic Hybrids Work. Ed. Jamie P. Deaton. EPA, 11 Apr. 2008. Web. 15 Nov. 2010. <http://auto.howstuffworks.com/hydraulic-hybrid.htm>. 2 Clean Automotive Technology. Innovation that Works. EPA, June 2006. Web. 10 Oct. 2010. <http://www.epa.gov/oms/technology/recentdevelopments.htm>.



3. Design Norms Christians are called to live lives that are “holy and pleasing to God” (Romans 12:1). As followers of Christ, the team holds certain moral standards and guidelines in everything that they do. In light of this fact, the senior design project will have specific moral guidelines that will be followed. These moral guidelines, as associated with engineering design, are called design norms. The design norms that have been selected for this project are: stewardship, trust, and transparency. Colossians 3:23-24 helped guide the team when choosing these design norms to govern the project. The passage explains that “whatever you do, work at it with all your heart, as working for the Lord, not for men… It is the Lord Christ you are serving.”

3.1 Stewardship Christians strive to be conscious of the gifts God has given them, not only the physical things, but also the less tangible gifts of time and talent. It is not necessarily a Christian ideal to make a product that is more efficient; however, the team believes they should use the resources given by God to the best of their abilities.

3.2 Trust The design will be safe and trustworthy. The hydraulic system will, again, be dependable, reliable and consistent so that a customer will be able to trust it. This will be done by implementing safety measures such as seat belts and a redundant braking system in the event of a hydraulic component failure. Without this trust, a sense of doubt lies in the product and the team desires to obtain a user’s complete satisfaction and confidence.

3.3 Transparency The design will be transparent so that the control of this system will function as intuitively as possible. It will be controlled by gas and brake pedals so that any new user will be familiar with its control. The design of the hydraulic system will in no way hinder the performance or integrity of the vehicle. Not only will our system be predictable in use, it will be reliable and consistent.



4. Project Management In order to complete the project on time, a scheduled work breakdown structure and a Gantt chart were constructed. These documents can be found in Appendix A. The deadlines outlined in these documents were followed as closely as possible to ensure a timely project completion.



5. Overall System The overall system has several requirements set by the project goals. To meet these requirements, the overall system will include a hydraulic system that will enable regenerative braking, a primary gasoline engine, and a control system. The prototype will undergo a set evaluation process to verify the project goals have been met.

5.1 Requirements The proposed hydraulic hybrid system will primarily focus on improving the energy efficiency of the vehicle it is implemented on by 40%. It will also safely accelerate and decelerate at a rate of 5.3 ft/s2 and achieve a maximum speed of 20 mph. The system will provide the user with a safe and comfortable operating environment that a driver is accustomed to. More specifically, the user will not be able to distinguish that the vehicle functions using a hydraulic hybrid system. This prototype vehicle and its testing will be completed in time for the Calvin College Engineering Banquet on Saturday, May 7, 2011.

5.2 Design Process The process for designing the overall system started with the development of a few major requirements and specifications about the project. Design alternatives for each subsystem of the project were then considered and analyzed both individually and in reference to the entire project.

5.3 Proposed Design The proposed design is a series hydraulic hybrid system, shown in Figure 1 that will be implemented on a donated golf cart. Series systems do not have the typical driveshaft or transmission of that a ‘normal’ vehicle has, as the hydraulic system itself powers the turning of the wheels. By reducing the number of components necessary, energy inefficiencies can be



limited.

Figure 1: Series Hydraulic Hybrid System

A major benefit of a series hybrid system is that the engine is able to run at its optimum efficiency. Running the motor at the most efficient speed lowers the amount of fuel consumed and emissions released to the atmosphere. Additionally, the engine may be turned off or idled when the accumulator contains sufficient pressure.

Another major benefit of the design is the regenerative braking capabilities. When a standard vehicle’s brakes are applied, friction slows and ultimately stops the rotation of the wheels. The result of this action is the kinetic energy of the vehicle being converted to frictional heat, a type of energy that cannot be captured in this application. The proposed regenerative system captures the kinetic energy to power the hydraulic drive motor which in uses backpressure from the accumulator as resistance to slow down, shown in Figure 3. This pressurized fluid then may be released to drive the hydraulic drive motor assisting in accelerating the vehicle once again.

5.4 Feasibility Due to the market research that has been conducted, the project goal of a 40% increase in fuel efficiency is attainable. The team believes that it has conducted enough analysis and calculations, found in Appendix B and Appendix C, to design a functioning system that will operate smoothly with the desired results and safety measures.

5.5 Evaluation Process To test and evaluate the goal of achieving 40% better fuel economy with the prototype vehicle, a baseline number will be developed for the vehicle’s fuel efficiency without the use of the hydraulic drive system. The vehicle will first be built using a gasoline motor and a standard centrifugal clutch and belt drive, as seen in Figure 2. With this arrangement, the team will drive

Low-Pressure Accumulator

Pump/ Motor

High-Pressure Accumulator

Hydraulic Drive

Assembly



the vehicle under a set range of operating conditions to develop a baseline value of fuel efficiency.

Gasoline Engine

Belt

Centrifugal Clutch

Final Drive Assembly

Figure 2: Diagram of Baseline Drive System

After this initial testing is complete, the drive train will be converted into the hydraulic drive system as shown in Figure 3. The vehicle will be driven as a series hydraulic hybrid under the same set operating conditions to gather data for the hydraulic hybrid’s fuel efficiency. With these two sets of data, calculations can be made to determine if the goal of achieving 40% better fuel efficiency was met.

Gasoline Engine

Final Drive Assembly

Hydraulic Line

Hydraulic Motor

Hydraulic Pump

Figure 3: Diagram of Hydraulic Drive System



6. Vehicle Chassis The chassis of the vehicle is important because it is the foundation of the entire vehicle. A successful project starts from a solid base. The major design requirements for the chassis of the prototype vehicle are its ability to hold four passengers comfortably while supporting the series hydraulic system and regenerative braking components. The chassis must also allow for a conversion from a normal drive system to the hydraulic drive system for testing purposes. The vehicle must be able to function as a normal vehicle would in terms of rider quality, performance, and safety.

6.1 Requirements The chassis design is guided by a set of basic requirements that must be met by any design alternative considered.

6.1.1 Strength The vehicle’s frame must be strong enough to support the weight of the riders and drive train components without risk of failure or excess flexure.

6.1.2 Size The frame must be large enough to accommodate four riders. The frame must also be in the relative size range of a standard golf cart as this is the scope of the project.

6.2 Design Procedure When considering options for the platform of the vehicle, two basic options present themselves. The first is to build a vehicle frame from scratch. This involves designing, machining, and fabrication of the frame. The second option is to utilize an existing vehicle and modify it for the project’s purposes.

6.2.1 Design Alternatives The first alternative to build a frame from scratch has the unique benefit that it could conveniently be designed and built completely to desired specifications. The drawback to building the frame is that it requires a lot of design time and fabrication time and may take away from the heart of the project: the design and implementation of hydraulic hybrid system.

The second alternative, to utilize an existing frame and customize it to the project’s needs, is beneficial because a lot of the necessary project components would already be in place. The steering and suspension systems already present on the vehicle may be used as a platform to build upon. The drive system of the existing vehicle would need to be taken out and modified, but this would allow for the primary focus of the team’s efforts to be on the hydraulic system. A drawback to using an existing vehicle as a frame platform is that it will reduce the flexibility in placing and supporting the drive system components.



6.3 Proposed Design The proposed design for the prototype vehicle’s chassis is to follow the second design alternative and use an existing chassis as a base for the vehicle. This will allow the team’s focus to be on the design and implementation of the vehicle’s hydraulic system. A suitable vehicle to start with will be a used golf cart with most of its mechanical systems operational.

6.4 Financials The base vehicle used for the prototype will be obtained at no charge to our group through a donation or junk yard salvage.



7. Hydraulic System The hydraulic system is the key component to propel the vehicle and store energy when braking. It consists of five main components, and is governed by a system of valves.

7.1 Components The hydraulic system is comprised of 4 major components:

Hydraulic Pump: The hydraulic pump moves hydraulic fluid from low to high pressure. Its main purpose is to charge the accumulator.

Accumulator: A high pressure accumulator stores incompressible hydraulic fluid under high pressure by a compressible gas bladder filled with nitrogen gas.

Hydraulic Drive Motor: The hydraulic drive motor translates high pressure hydraulic fluid to rotational motion used to turn the wheels. When braking, the hydraulic drive motor acts as a pump, and uses back pressure as resistance while moving hydraulic fluid into the accumulator to decelerate the vehicle.

Low Pressure Reservoir

7.2 Requirements

: A low-pressure reservoir serves as a low (atmospheric) pressure storage tank for hydraulic fluid.

The system must have enough power to accelerate and decelerate the vehicle with four people at the aforementioned nominal rates. This would include the proper sizing of all pumps, motors and engines, as well as proper flow through all tubing and valves. The accumulator must also be able to store enough fluid under pressure to propel the vehicle to a maximum speed and maintain that speed for at least 10 seconds.

7.3 Gearing The ideal situation would allow for the pump and motor to be connected to their systems directly. The overall system may need a gearing system to reduce the actual torque or speed of the wheels or a gasoline engine to either the hydraulic pump or the hydraulic drive motor. If needed, this will be implemented through the design and use of a gearbox, series of chains and sprockets, or a series of belts and pulleys.

7.4 Design Procedure The design procedure involves modeling the system by applying the law of conservation of energy. Using this, the system can theoretically be proven to show an energy savings through Engineering Equation Solver (EES). Calculations performed in Simulink also can be used to calculate energy savings as well as assist with system sizing.



7.4.1 EES Calculations A simple analysis of the hydraulic system is modeled using the EES program. A complete illustration of these calculations is found in Appendix B. This analysis uses the principles of thermodynamics and energy conservation to calculate the energy stored under pressure in the accumulator within a specified time period. The results show the ability to regain, through braking, roughly 70% of the initial energy put into the vehicle. Figure 4 models the vehicle going through acceleration, braking, and then reacceleration using the energy stored when braking. Because of the way the acceleration and braking models were linked, it was difficult to smoothly transition the accumulator pressure between time intervals around a velocity of zero.

Figure 4: Varying Accumulator Pressure with Velocity of the Vehicle

It should be noted that these calculations only incorporate the inefficiencies in the hydraulic pump and hydraulic drive motor and do not include head loss, drag force or other frictional forces the vehicle will experience. To better account for these inefficiencies, the system was modeled in Simulink, as discussed in the next section.

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7.4.2 Simulink Calculations A more complex model of the entire system was analyzed through Simulink-SimScape. This program modeled the hydraulic system and simulated driving the vehicle. The comprehensive Simulink schematic of the system can be found in 0. The simulation shown below begins with the gasoline motor running and charging the accumulator for 20 seconds. At a time of 30 seconds, the drive valves are engaged and the vehicle accelerates for 10 seconds. The vehicle then coasts for 10 seconds. The braking valves are then engaged and the vehicle decelerates for 7 seconds, recharging the accumulator. The vehicle is then accelerated for the remainder of the simulation. Graphs of the accumulator pressure and vehicle velocity are presented in Figure 5 and Figure 6 below.

Figure 5: Graph of Accumulator Pressure (psi) vs. time (s)

Accu

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Figure 6: Vehicle Velocity vs. Time

The important part of this simulation for testing the performance of our system happens in the time range of 50 seconds to 70 seconds. At a time of 50 seconds, the brake valves are engaged and the vehicle slows down. As shown in the close up view on the pressure graph, this braking increases the pressure in the accumulator. The pressure increases from around 375 psi to about 405 psi. During the next acceleration phase, the pressure in the accumulator decreases. It takes around 4 seconds for the accumulator pressure to drop below 375 psi, the initial charge of the accumulator before recapturing any energy. This means that four seconds of our acceleration utilized the recaptured energy from braking. Braking slowed the vehicle from about 9 mph to 2.6 mph. The first four seconds of acceleration accelerated the vehicle from 2.6 mph to 6.5 mph. The percent of energy recycled is calculated as seen below.

𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸 𝑅𝑅𝐸𝐸𝑅𝑅𝐸𝐸𝑅𝑅𝑅𝑅𝐸𝐸𝑅𝑅 % =6.52 − 2.62

92 − 2.62 = 48%

The results from this simulation confirm that an increase in fuel efficiency through regenerative braking is possible. This simulation will be updated as components are acquired.

Vehi

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Figure 7: Close-Up of Accumulator Pressure Graph

Figure 8: Close-Up of Vehicle Velocity Graph

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7.4.3 Design Alternatives A design alternative for the hydraulic system would be to implement a parallel hydraulic system instead of a series hydraulic system. A parallel system allows for the vehicle to primarily use a gasoline engine to directly power the vehicle and a hydraulic system is used to only recapture the energy dissipated in braking to accelerate the vehicle. A parallel system is far more complex because it involves a drive system that allows the user to use the primary engine hydraulic system or a combination of the two to accelerate. The team decided that a series system was not only a more progressive technology, but it will be able to be implemented in a more transparent manner. Additionally, the scope of a series system would better correspond to the time given to design and build a prototype vehicle.

7.5 Proposed Design The proposed design is a series hydraulic system that utilizes a primary gasoline engine, a hydraulic pump, an accumulator, and a reversible hydraulic motor. The vehicle will be driven by hydraulic fluid and decelerated by utilizing the backpressure and the hydraulic drive motor to pump fluid back into the accumulator.

7.6 Feasibility The EES and Simulink analyses confirm a significant amount of energy can be recycled through regenerative braking.



8. Primary Power Source The scope of the project entails the primary power source of the system to be a gasoline engine. Therefore, the performance of the prototype can be compared easily to a larger vehicle, such as a mail delivery truck as well as increase the range of the proposed vehicle. Also, this will achieve the goal of retrofitting the hydraulic system in existing gas powered vehicles.

8.1 Requirements Requirements on the primary engine that need to be held for each design alternative considered.

8.1.1 Power, Torque, and Speed The hydraulic pump sets two main requirements for the gasoline engine:

Shaft speed: The pump operates most efficiently at a certain shaft speed; therefore, the gasoline engine must also operate efficiently near that speed.

Shaft torque

If the engine used in the prototype cannot output the required shaft speed and torque, an intermediate gear system will be used; however, implementing an intermediate gear system would cause the vehicle to perform more inefficiently.

: The pump requires a minimum torque input to the shaft. The gasoline engine is required to output enough torque to the pump shaft.

Based on these requirements, the power output range can be determined for the gasoline engine. The motor also must output enough power directly to the wheels to accelerate the vehicle. This is because the evaluation procedure involves powering the vehicle without the series hydraulic system in order to determine the baseline efficiency before the retrofit. A brief explanation of this evaluation method is found in Section 5.5.

8.1.2 Engine Dimensions The prototype vehicle is small; therefore, the physical size of the engine is of concern. The engine must be small enough so that there is room for all the other components in the hydraulic system to fit, but also large enough to provide the necessary power.

8.2 Design Procedure First, the required power to accelerate the vehicle was calculated. Next, the hydraulic system was modeled using EES. The hydraulic system model calculated a range for the required power, torque, and shaft speed of the primary motor. The group will then select a gasoline engine that falls within the necessary power, torque, and speed ranges.



8.2.1 Calculations A force balance was used to estimate the required power to accelerate the vehicle to a top speed of 20 mph with just the gasoline engine as described in section 5.5. The calculations were based on nominal and worst case driving scenarios. For both cases, the vehicle was assumed to weigh 1400 lbs, having a wheel radius of 6 inches, a rolling resistance of 0.022, and able to accelerate at a rate of 6 ft/s2. The nominal case assumed that the vehicle would accelerate on flat ground. The worst case assumed the vehicle would accelerate up a 6% grade hill. The nominal power output estimate for the engine was 5.9 hp, while the worst case power output estimate for the engine was 7.9 hp. A copy of the equation sheet can be found in Appendix D.

8.2.2 Design Alternatives A design alternative for the primary gas motor is an electric motor. The electric motor would run off of electric energy stored in a battery bank. This design option was not selected for several reasons. First, the vehicles range would be limited by the capacity of the battery bank. Second, the batteries would take up a large amount of space on the vehicle, and third, batteries would significantly increase the weight and the costs of the prototype.

8.3 Proposed Design For the prototype, the group will seek a gasoline engine of roughly 8 hp by donation. Once the engine is obtained, the group will perform tests to determine the optimum efficiency of the engine. The tests will involve connecting the engine to a dynamometer, applying a load equivalent to the load of the hydraulic pump, and varying the throttle. A power curve for the engine will be constructed to determine the shaft speed that optimizes power output. Also, the fuel consumption at each throttling position will be recorded to determine the most fuel efficient throttle position relative to power output.

8.4 Financials The group will seek a donor for the primary engine; however, if a donor cannot be found, a portion of the budget will be used to purchase the gasoline engine.



9. Controls System The control system has a significant impact on the safety and overall efficiency of the vehicle. The proposed hydraulic system includes a high pressure accumulator, which can reach unsafe pressure levels if it is not properly managed. Also, a major advantage of a series hydraulic hybrid system is the ability to run the gasoline motor at optimum efficiency when power is required, which improves the overall efficiency of the vehicle. In order to design a safe vehicle and obtain a 40% increase in fuel efficiency, a control system must manage the accumulator pressure and engine throttle.

9.1 Requirements The control system must manage the accumulator so that the internal pressure never reaches a dangerous level. The hydraulic system requires a minimum operating pressure in the accumulator to properly function. To ensure the accumulator pressure stays in the operating pressure range, the control system must manage the engine so when the pressure reaches the upper limit, the engine throttle is reduced to idle or is shut off completely. When the pressure in the accumulator approaches the lower limit, the control system must increase the engine throttle to the optimum operating speed or restart the engine and throttle it to the aforementioned operating speed.

9.2 Design Procedure A model of the vehicle was created using Simulink which contains pre-defined blocks to model pressure relief valves, controller devices, and other hydraulic components. Simulink was used to design and test the engine throttle control system, and to ensure the pressure in the accumulator never reached an unsafe level.

9.2.1 Calculations The Simulink model was used to simulate operating conditions where the control system must react. The control system includes a pressure transducer and a relay device. The pressure transducer senses the pressure level in the accumulator and sends a signal to a relay device. The relay block manages the engine throttle by comparing the pressure signal to an upper and lower threshold limit. When the upper limit is reached, the relay signals the throttle to shut the engine off or to throttle down. When the lower limit is reached, the relay signals the engine to restart or throttle up to the most efficient operating speed. In order to see the results of braking clearly, the modeled engine was always shut off when the vehicle was braking. Another component of the controls system is a mechanical safety valve. The high pressure release valve was placed between the high pressure accumulator and the low pressure reservoir for redundancy. The valve is preset to open at an upper safety limit of 3000 psi.



The simulation begins with the gasoline engine charging the accumulator for 60 seconds. This is enough time for the pressure in the accumulator to reach the upper limit. In the time range 60 seconds to 170 seconds, the vehicle accelerates, which uses some of the high pressure fluid. A graph of the accumulator pressure as a function of time is shown in Figure 9.

Figure 9: Controlled Accumulator Pressure

Figure 9, above, shows that the designed control system fulfills all the requirements. The mechanical safety valve opened when the accumulator pressure reached the upper safety limit of 3000 psi at t = 20 s. Also, when the safety valve opened, the engine is shut off. After the vehicle began to constantly accelerate at t = 60 s, the pressure in the accumulator decreased to the lower threshold value of the relay at t = 75 s. The motor was then restarted and remained running until the accumulator pressure reached the high threshold value.

9.2.2 Design Alternatives A design alternative for the control system modeled above is a user interfaced control system, which would consist of an accumulator pressure gauge and an engine starter. With this system, the user would be required to start and shut off the engine based on the pressure gauge. This design alternative was not pursued because this option did not comply with the set design norms as the vehicle would no longer by operated in a simple manner.

Accumulator Pressure

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On/Off



9.3 Proposed Design For the prototype vehicle, the proposed control system design would include a pressure relief valve placed between the accumulator and the low pressure reservoir that would open when the pressure in the accumulator became too high. Also, a pressure transducer, relay, and a mechanical actuator would be used to control the engine throttle, allowing the engine to shut off when power is not required.



10. Drivers Comfort and Safety

10.1 Comfort The vehicle will fit four adults (including the driver) safely and comfortably. The seats will be of proper size and have adequate support for the users. A windshield will be in place to give the driver and passengers more comfort when traveling at higher speeds and warmth during the colder seasons.

10.2 Safety The vehicle will have hand rails as well as proper feet support to help stabilize the passengers while the vehicle is in motion. It will have a proper vibrational dampening system to ensure a safe and smooth ride. Additionally, there will be a redundant braking system so the operator will be able to safely stop the vehicle in the event of a failure in the primary hydraulic braking system.



11. Business Financials

11.1 Prototype Cost The vehicle prototype will cost an estimated $1,658 to build; however, the team is investigating donors to reduce the prototype cost. This, in part, is due to high costs of the hydraulic components that will be used. This estimated cost is a worst-case scenario, where none of the components are donated or significantly discounted. A detailed outline of the prototype budget is found in the Appendix E.

11.2 Retrofit System Cost and Selling Price Appendix F contains information related to cost and selling price of a retro fit hydraulic hybrid system. The total variable cost of the retrofit system is $5,063 per unit. The calculated selling price for the system is $8,405, based on a 66% mark-up.



Appendix Table of Contents

Appendix A: Work Break-down Structure and Gantt Chart ......................................................... 25

Appendix B: Hydraulic System EES Model .................................................................................... 28

Appendix C: Hydraulic System Simulink Model ............................................................................ 32

Appendix C: Primary Engine EES Model ....................................................................................... 33

Appendix D: Prototype Budget ..................................................................................................... 35

Appendix E: References ................................................................................................................ 35



Appendix A Work Break-down Structure

Task Name Date Due Person Assigned Project Definition

Project Scope 9/27/2010 Team Problem Definition 9/27/2010 Team Goals/Objectives/Requirements 9/27/2010 Team Preliminary Budget 10/1/2010 Team

Scheduling Work Break Down Structure 10/8/2010 Liz/Jay Schedule Work Break Down Structure 10/18/2010 Jay Gantt Chart 10/25/2010

Research Market Research 10/18/2010 Jon Project Feasibility 10/28/2010 Tim, Zach, Liz Design Options 10/18/2010 Jay Component Cost 11/1/2010 Team

Feasibility Calculations Base Case Analysis 11/1/2010 Team Efficiency Range Capabilities Energy Analysis 11/1/2010 Team Braking Accelerating Normal Drive

Design Overall System Option Identification 10/18/2010 Jon Identification Research Evaluation/Selection

Prototype Design & Component Selection 11/1/2010 Tim, Zach, Liz, Jay

Vehicle Chassis Tim Hydraulic System Zach, Liz Primary Power Source Jay Controls System Jon

Optimization 11/28/2010 Team

Efficiency Range



Evaluation/ Comparison 11/21/2010 Team Efficiency Range Capabilities

Budget Prototype Component Selection 11/28/2010 Team

Presentations Preliminary Presentation 10/13/2010 Zach Elevator Pitch 10/20/2010 Jon Oral Presentations Website 10/25/2010 Liz

PPFS Report Table of Contents 10/4/2010 Introduction Jon Market Research Jon Design Norms Jon Overall System Tim Vehicle Chassis Tim Hydraulic System Zach, Liz Primary Power Source Jay Controls System Jay, Tim, Jon Driver Comfort/Safety Zach Business Financials Liz, Jay Conclusion Team Appendix Assembly/ Formatting of PPFS Draft 11/15/2010 Final 11/29/2010 Preliminary Design Memo 12/10/2010

Hydraulic Hybrid 27


Appendix A Gantt Chart

Ta

sk N

ame

Dur

atio

nSt

art

Fini

shPr

edec

esso

rsR

esou

rce

Nam

es

Proj

ect D

efin

ition

18 d

ays?

Wed

9/8

/10

Fri 1

0/1/

10Pr

ojec

t Sco

pe14

day

s?W

ed 9

/8/1

0M

on 9

/27/

10Pr

oble

m D

efin

ition

14 d

ays?

Wed

9/8

/10

Mon

9/2

7/10

Goa

ls/O

bjec

tives

/Req

uire

men

ts14

day

s?W

ed 9

/8/1

0M

on 9

/27/

10Pr

elim

inar

y Bud

get

5 da

ys?

Mon

9/2

7/10

Fri 1

0/1/

101

day?

Mon

8/3

0/10

Mon

8/3

0/10

Sche

dulin

g38

day

s?W

ed 1

0/27

/10

Sat 1

2/18

/10

Wor

k Bre

ak D

own

Stru

ctur

e1

day?

Wed

10/

27/1

0W

ed 1

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/10

Sche

dule

Wor

k Bre

ak D

own

Stru

ctur

e1

day?

Wed

10/

27/1

0W

ed 1

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/10

Gan

tt C

hart

38 d

ays?

Wed

10/

27/1

0Fr

i 12/

17/1

0

Res

earc

h38

day

s?Th

u 9/

9/10

Mon

11/

1/10

Mar

ket R

esea

rch

28 d

ays?

Thu

9/9/

10M

on 1

0/18

/10

Proj

ect F

easa

bilit

y24

day

s?M

on 9

/27/

10Th

u 10

/28/

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esig

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ptio

ns16

day

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on 9

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on 1

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/10

Com

pone

nt C

ost

26 d

ays?

Mon

9/2

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Mon

11/

1/10

Feas

abili

ty C

alcu

latio

ns1

day?

Mon

8/3

0/10

Mon

8/3

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Bas

e C

ase

Anal

ysis

19 d

ays?

Wed

10/

6/10

Mon

11/

1/10

Effic

ienc

y19

day

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ange

19 d

ays?

Wed

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6/10

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Cap

abili

ties

19 d

ays?

Wed

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Ener

gy A

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day

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19 d

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Wed

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Ran

ge19

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apab

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ign

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l Sys

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ion

Iden

tific

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on 9

/27/

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on 1

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/10

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tific

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day

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/27/

10M

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/10

Res

earc

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day

s?M

on 9

/27/

10M

on 1

0/18

/10

Eval

uatio

n/Se

lect

ion

16 d

ays?

Mon

9/2

7/10

Mon

10/

18/1

0Pr

otot

ype

Des

ign

& C

ompo

nent

Sel

ecti

10 d

ays?

Tue

10/1

9/10

Mon

11/

1/10

Vehi

cle

Cha

ssis

10 d

ays?

Tue

10/1

9/10

Mon

11/

1/10

Hyd

raul

ic S

yste

m10

day

s?Tu

e 10

/19/

10M

on 1

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imar

y Po

wer

Sou

rce

10 d

ays?

Tue

10/1

9/10

Mon

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1/10

25

811

1417

2023

2629

25

811

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2629

14

710

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2528

14

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Oct

ober

201

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ovem

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Dec

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r 201

0

Hydraulic Hybrid 28


Appendix B Hydraulic System EES Model

Hydraulic Hybrid 29


Hydraulic Hybrid 30


Hydraulic Hybrid 31


Hydraulic Hybrid 32


Appendix C Hydraulic System Simulink Model

Hydraulic Hybrid 33


Appendix D Primary Engine EES Model

Hydraulic Hybrid 34


Hydraulic Hybrid 35


Appendix E Prototype Budget Prototype Materials and Supplies

Part Description Quantity Prototype Cost Production

Cost

Bi-rotational Pump 1 $300.00 $200.00

Gear Pump 1 $200.00 $150.00

5 Gallon Accumulator 1 $500.00 $300.00

Hydraulic Hose 50 feet $10.00 $10.00

Hydraulic Fluid 5 Gal $50.00 $40.00

Check Valves 4 $30.00 $20.00

Three-way Valves 2 $0.00 $30.00

Pressure Gauge 1 $8.00 $5.00

Pressure Relief Valves 2 $15.00 $10.00

12-16 hp engine 1 $75.00 $60.00

Disc Brakes 4 $20.00 $40.00

Spur Gears 3 $100.00 $100.00

Frame 1 $100.00 $100.00

Total $1,408.00 $1,065.00

Hydraulic Hybrid 36


Appendix F Business Financials

Variable and Fixed Costs of Operation

Variable Costs (per unit)

Materials and Supplies

Part Description Quantity

Production Cost

Bi-rotational Pump 1 $600.00

Gear Pump 1 $450.00

Accumulator 1 $900.00

Hydraulic Hose 50 feet $30.00

Hydraulic Fluid 15 Gal $120.00

Check Valves 4 $60.00

Three-way Valves 2 $90.00

Pressure Gauge 1 $15.00

Pressure Relief Valves 2 $30.00

Spur Gears 3 $300.00

Frame 1 $300.00

Total $2,895.00

Labor Costs

Description Hours

Per Vehicle Cost

Fabrication 10 $1,000.00

Total $1,000.00

Total Variable Cost of Goods Sold

$3,895.00

(Materials, Labor, and Manufacturing Overhead)

Company Expenses (30% overhead percentage)

Shipping & Delivery

$200.00

Research and Development

$200.00

Accounting

$200.00

Marketing

$200.00

Sales

$200.00

Warranty Repairs

$168.50

Hydraulic Hybrid 37


Total

$1,168.50

Total Variable Costs

$5,063.50

System Selling Price (66% Mark-up) $8,405.41

Fixed Costs

Product Design

Description Hours Cost

Design and Feasibility 75 $7,500.00

Facilities

Land/Building

$39,333

(payment over 15 years)

Total Fixed Cost Of Goods Sold

$46,833.33

(Building and Manufacturing/Design Salaries)

Salaried Employees

$195,000.00

Advertising

$5,000.00

Total Fixed Operating Costs

$200,000.00

Total Fixed Costs

$246,833

Hydraulic Hybrid 38


References

How Hydraulic Hybrids Work. Ed. Jamie P. Deaton. EPA, 11 Apr. 2008. Web. 15 Nov. 2010. <http://auto.howstuffworks.com/hydraulic-hybrid.htm>.

Clean Automotive Technology. Innovation that Works. EPA, June 2006. Web. 10 Oct. 2010. <http://www.epa.gov/oms/technology/recentdevelopments.htm>.

Auto Blog & Auto Gallery. Niotauto, 30 Dec. 2010. Web. 12 Oct. 2010. <http://blog.niot.net/blog-images/30_Dec/eaton-developing-hydraulic-hybrid-systems.jpg >.

project proposal and feasibility study (ppfs)

Documents