Multidisciplinary Senior Design ConferenceKate Gleason College of Engineering

Rochester Institute of TechnologyRochester, New York 14623

Project Number: P15280

RIT HOT WHEELZ POWERTRAIN TEST BENCHDECEMBER 10TH, 2015

Maura ChmielowiecMechanical Engineering

Henry LeiElectrical Engineering

Jennifer SmithMechanical Engineering

Vladimir KravljacaElectrical Engineering

Eric PaternoMechanical Engineering

Dixon WongElectrical Engineering

ABSTRACTThe RIT Hot Wheelz Formula SAE Electric team expressed a strong need to test their electric powertrain

system prior to assembling it to a rolling chassis to ensure the. From this need, a Senior Design Project set out to develop a powertrain test bench to validate system safety and collect data while applying a load to the powertrain motor prior to assembling on the chassis. Using a pre-existing dynamometer system with the Kate Gleason College of Engineering, mechanical systems were created to interface to the existing hardware and a method to communicate and collect data from the systems was developed. Overall, the project resulted in a usable test platform that can be utilized to apply a load to the powertrain and collect data over a period of time to help the team test their systems safety and tune the powertrain before installing it on a rolling chassis.

NOMENCLATURE DAQ – Data Acquisition DUT – Device Under Test GUI – Graphical User Interface KGCOE – Kate Gleason College of Engineering NI – National Instruments PCB – Printed Circuit Board RMS – Root Mean Square RPM – Revolutions Per Minute SME – Subject Matter Expert USB – Universal Serial Bus

INTRODUCTION The RIT Hot Wheelz Formula SAE Electric team is a group of all-female undergraduate engineering students

who come together to form a team of innovative and creative race enthusiasts. Their focus is an environment of both learning and teaching with hands-on design and build experience. Previously, the team had competed in only RIT-specific events at Imagine RIT. Over the past 4 years, they have competed in an Electric Dragster Competition in

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2012 (1st Place), an Electric Endurance Competition in 2013 (3rd Place and the Innovation Award), and an Electric Autocross Competition in 2013 (3rd Place). Due to the high level of performance and achievement during these previous competitions, the Hot Wheelz team was ready to take their skills to the next level and enter into a more rigorous competition. The team is now designing and building a new car from the ground up to enter into the 2016 Formula Hybrid competition in the electric-only category.

With this goal in mind, the Hot Wheelz team desired a way to test their electro-mechanical drive system before it is installed on their chassis. The electro-mechanical drive system includes an electric motor, batteries, a motor controller and other small electrical components within the circuit. Therefore, the purpose of this project was to build a powertrain test bench capable of testing the electro-mechanical drive system of the Hot Wheelz vehicle. Utilizing the test bench, the Hot Wheelz team will be able to verify the safety and performance of their electrical system prior to the system being installed on their chassis.

The main requirements were a user friendly, portable system with easy set-up and teardown. It must remain modular to allow flexibility in the unit under test. A controlled load must be applied to the electric motor without overdriving the motor. Key electrical drive system performance data, such as torque output and battery life, are required to optimize the system capabilities. Safe operation of the electrical components, smooth integration of the completed drive system onto the chassis of the completed Hot Wheelz vehicle, and the ability to verify the system's compliance to the SAE rules were also desired.

PROCESS

During the design phase of MSD I, several concepts were evaluated and interfacing with the small-engine dynamometer in the KGCOE machine shop was selected. This would provide the highest feasibility of a completed project. Mechanical components were constructed around the existing platform and sprocket interface with the dynamometer. Serial communication was used to communicate with the dynamometer controller and an analog voltage throttle control was used to interface with the Hot Wheelz drive system under test.

Mechanical Design

I. Utilizing Existing EquipmentThe existing hole pattern in the platform and the dynamometer shaft was effectively utilized to reduce

design and construction required for mounting. Components to be mounted on the dynamometer platform utilize a 4” by 4” spacing of ⅜” holes. The design of the sprocket interfaces with the existing mount on the dynamometer shaft. This mounting is based around a bolt circle of 2.44” radius with 5 5/16” bolts and a 4” D clearance hole in the center.

II. Motor MountIn order to properly constrain the motor, a motor mount needed to be designed

to hold the motor in static and dynamic conditions. Initially the project was geared around the HPEV AC 35 specifications for size, weight, hole pattern and torque capabilities. The motor mount was designed out of ⅜” steel plate that mimicked the hole pattern and shape of the motor face and featured welded on legs with slots to properly affix the mount to the dynamometer and cart platform. The slot design was made to fit within a 4” by 4” hole pattern, with the slots being 12” apart. Due the nature of an electric motor, the motor mount needed to withstand a dynamic loading of 108 ft./lbs. instantaneously from the end of the motor shaft as well as holding the 85 lbs. motor statically over a long period of time without deformation. The motor mount was validated using Finite Element Analysis but was never able to be tested physically since the project changed slightly to what will be called “Plan B”. Within “Plan B” a pre-existing ¼” steel motor mount with a 65 lbs. motor was used. The motor mount did not show any signs of failure or fatigue through physical testing.

Project P15280

Figure 1: Motor Mount with Hot Wheelz Motor

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III. Powertrain CartA key design requirement was portability. The system must be transported to

the dynamometer, located in the Mechanical Engineering machine shop, easily set-up, and easily removed when testing was complete to allow shared usage of the facility. With that in mind, a cart system was designed to house all components, including the Hot Wheelz powertrain system, and allow for easy transportation. The base cart was sourced based on weight limit and the available space in the dynamometer room. In addition to the base cart, a motor mount and battery mounting platform were designed out of Premium Douglas Fir wood and hardwood plywood to utilize feature of the cart. A secondary handle was purchased and modified to hold a T-shaped panel which housed and transported the motor. The mount also had a 4” x 4” hole pattern to align with the motor mount created. Structural support gussets were added to the panel to eliminate vibrations during transportation. In order to utilize space effectively, and imitate the

actual layout of the system on the vehicle, a battery platform was designed to house the battery enclosures on the middle of the cart and mounted upright. Both platforms were assembled using a Kreg tool to get precise and strong joints.

IV. Power Transmission SystemAn ANSI 50H chain transmits torque between the Hot

Wheelz electric motor and the dynamometer. The chain tensioner was designed with observation of the shortcomings of the chain tensioner used by the Formula Team. It was observed that the process of adjusting the height of the idler sprocket to increase chain tension was both laborious and inconvenient. An increase in usability while maintaining robustness was desired. Machining parts for the chain tensioner was accomplished with the water jet, mill, and lathe in the machine shop. The final design meets usability and robustness considerations. The idler sprocket can be adjusted and securely fixed at a new height in under one minute.

V. Safety Considerations The chain was selected to withstand a load far beyond the maximum load the Hot Wheelz electric motor is

capable of producing. The chain is rated for a static load of 1620 lbs. and the electric motor can produce a maximum load of 1150 lbs. This means that the chain would not fail even if dynamometer were to lock up and remain static. During testing, a webcam is used to monitor the status of mechanical system components. This ensures that action can quickly be taken to stop the test if an unexpected failure occurs. Additionally, the cart sourced was rated to hold 1000 lbs. which is approximately double the max weight the cart was designed to see, including the powertrain system.

Electrical Design

I. Hardware SetupThe hardware setup for the test bench includes the following: an AC to DC power supply, a customized

power distribution PCB, and finally various sensors that senses the necessary metrics per the engineering require to provide feedback to the GUI. A DC output of 24 V from the main power supply was selected in order to provide sufficient voltage for the high rating voltage sensors. The AC-DC power supply is connected to the customized PCB via keyed 2-Pin Molex connectors to ensure correct installation between the two items.

A Schottky diode was placed immediately after the 24 V voltage source to avoid damage to additional components in the case of incorrect installation, i.e. reversed polarity. Voltage supplied to the voltage sensors is then taken from that node, which is at roughly 23.7 V. Following the output of the voltage sensors, a 10 V regulator was then put in series to provide the voltage needed for the current sensors.

Finally, the PCB and the AC-DC power supply were packaged into one enclosure, with the AC-DC power supply on the outside of the enclosure. The power supply was mounted on the outside of the enclosure for two

Copyright © 2015 Rochester Institute of Technology

Figure 2: Powertrain Cart without Powertrain

Figure 3: Chain and Chain Tensioner System

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specific reasons: the first one being that the user will be able to see whether it’s functioning or not by looking at the green LED indicator located on the power supply; and the second one being that the physical enclosure will provide additional noise isolation.

For simplicity of use and modular functionality, the electrical enclosure only requires one connection to the wall, while all other connections to the sensors can be deployed via key connectors again to ensure no chance of incorrect usage.

Two additional main electrical hardware components were utilized in this project: the first one being the emergency-stop setup and the second one being the connection between the I/O’s of the DAQ and the devices that it connects to. For the emergency-stop, a three way harness was made to interface with the DAQ and the two emergency switches in both rooms. For the throttle control, lugs and the appropriate connectors were installed to interface with the DUT motor controller, and BNC to Molex connectors were installed for correct interfacing between the harness and the DAQ such that the two can communicate effectively.

II. SensorsAs stated in the introduction, the test bench is built with the capability of monitoring and recording key

parameters such as voltage, current and temperature of both the motor and batteries. All sensors used in this project output an analog voltage that is read and interpreted by the NI DAQ. Torque and RPM readings can be directly read from the dynamometer controller and GUI. Individual test plans to test for the functionality of each sensor can be found through this link Detailed Test Plans .

A. Voltage CR-5310-600 DC voltage transducer (senses up to 600Vdc) and CR-4510-500 AC voltage transducer (Senses up to 500Vac rms) are used to monitor DC voltage from batteries and AC voltage from motor. However, due to time constraints sourcing the AC motor, the test bench currently monitors DC voltage from batteries and DC voltage from existing DC motor. The voltage transducers are Velcro mounted, therefore the CR-5310-600 DC voltage transducer is easily moved around to monitor DC voltage from both the motor and batteries. Both AC and DC voltage transducer require

24Vdc power source.

B. Current For current sensing, Honeywell CSLA2EL sensor is capable of sensing up to 550 Amps DC/AC and is used to monitor current from the battery and motor. Due to its easy to use open loop hall effect, the current sensor will sense current when the wire between battery and controller and/or wire between motor and controller is placed through the sensor. Due to the current sensor’s fragile pin design, special care is taken during mounting to minimize

Project P15280

Figure 4: Electronics & Power Distribution System

Figure 5: Voltage Transducer

Figure 6: Current Transducer

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stress on the pins by making an extra connector bridge between the connection of pin to connector and connector to DAQ. The sensor requires a 10Vdc power source.

C. Temperature

Figure 7: K-Type Thermocouple

K-type thermocouples are used to monitor the motor and battery temperature. One end of the thermocouple connects to the NI DAQ and the other end is a metal rod to monitor the desired temperature. The thermocouple to sense the motor is extended using a 15 feet k-type extension wire.

III. Data AcquisitionThe DAQ used is the NI CDAQ-9172, which interfaces through

USB. There are two NI-9215 analog input modules to capture the battery voltage, motor voltage, motor current, battery current, as well as an input for the emergency stop. Motor temperature and battery temperature data are acquired through the NI-9211 thermocouple module. Additionally, one analog output module is required to control the Hot Wheelz motor throttle, the NI-9263 analog output is capable of outputting up to 10 V; however, the Hot Wheelz motor controller is configured to accept a range from 0-5 V, which is configured through the GUI. Additionally, the dyno angular velocity and net torque are captured through serial communication with the

Dyne Controller. When the testing begins, a MATLAB window appears with the graphs of the acquired data displayed. The

dyno revolutions per minute, net torque as seen from the dyno, battery current, battery voltage, motor current, motor voltage, battery temperature and motor temperature are displayed. The angular velocity and net torque are sampled at approximately one sample per second, which isn’t sufficient enough to capture the necessary data. However, the analog inputs are sampled at a rate of 1000 samples per second, which is more than sufficient. As the samples are acquired and displayed they are additionally being recorded to a .csv file. This enables the user to analyze and interpret the results after the test has been completed.

IV. Graphical User InterfaceThe graphical user interface brings the whole system together by providing the user with the necessary

controls to perform a test. While the main program is written in Microsoft’s Visual Studio C#, the data acquisition is performed through MATLAB because of its real time graphing capabilities. Displayed in figure 1 is the high level GUI flow diagram. It is shown at the highest level due to the complexity of displaying simultaneous tasks performed through multi-threading.

The user is able to select between a manual test in which the Hot Wheelz throttle voltage, dyno RPM, and rate of change of the applied RPM can be varied by the user in addition to a simulated option where the user inputs the simulation profile in sequential order the values of the throttle position, dyno RPM, linear acceleration rate, and the duration for the profile to hold before moving onto the next.

After the test has completed the user is able to view the data recorded in a .csv file which can be opened in Microsoft Excel or MATLAB. Due to the amount of noise, the waveforms require filtering.

Copyright © 2015 Rochester Institute of Technology

Figure 8: NI CDAQ-9172

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Figure 9: High Level GUI Flow Diagram

RESULTS AND DISCUSSION Mechanical All constructed mechanical components described above interface with the existing dynamometer platform

with each other. The Hot Wheelz team electric motor can spin freely or against the resistance torque of the dynamometer. Chain tension is adjusted and maintained with the chain tensioner. A chain guard has been created and will be put in place to ensure safety when working in the dynamometer test cell in the future.

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Figure 10: Entire System Under Test

Electrical In terms of hardware, all components were functional as readings were able to be generated from sensors when

they are in use. The activation of emergency stops were able to disable the device under test 100% of the time. The Figure below is a sample of the torque output reading from the dyno, along with the current data captured from the sensor on the cart. The curves are consistent with each other, which validates the reading from the current sensor.

Figure 11 – Current and Torque Data Collected from Testing

CONCLUSIONS AND FUTURE RECOMMENDATIONS

Overall, the project was a success. The team was able to integrate Hot Wheelz’s electro-mechanical system with the Dyno varied rpm and torque in automatic and manual mode. The system is capable of monitoring and saving critical system information such as Torque, RPM, current, voltage and temperature. The Hot Wheelz team is satisfied with the delivered product and complimented it as easy to use.

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I. Mechanical Recommendations / Future Work Increasing modularity of dynamometer table. The KGCOE dynamometer is an excellent resource that

could be better utilized. Teams seeking to use the dynamometer should not be confined to a 4” by 4” hole pattern. This would be an effective single term design project.

Reduce height of Chain tensioner. The height of the chain tensioner means that its full range of adjustability is not being utilized. Also, the bearing shaft can interfere with the chain in some configurations. A solution is to machine approximately 1.5” off of the bottom of both side plates and re-drill and tap the appropriate mounting holes in the bottom of the side plates.

II. Electrical Recommendations / Future Work For more accurate temperature measurements, source a shorter thermocouple rod for K-Type

thermocouples and contact manufacturer for critical locations on battery/motor to monitor temperature. Add additional sensors and noise filtering Integrate the door of dyno-room into emergency shut-off circuit

ACKNOWLEDGMENTS The team would like to thank the following people for their advice and support of our project:

Marty Schooping: Hot Wheelz team advisor and customer for the test bench Hot Wheelz Team: Provided the funding Professor John Wellin: SME with sensors and NI equipment donation Vince Burolla: MSD I guide and SME for the EE team Gary Werth: MSD II guide and SME in project management Rob Kraynik and Jan Maneti: Gave ME team materials, assistance machining, and advice and feedback

on designs Dr. Marca Lam: Lent an analog module and DAQ for testing purposes Dr. Jason Kolodziej: Donation of materials Bill Finch: IT support Dr. Lyshevski for his input and knowledge on the topic of high power motors

Project P15280