2. Design Requirements The goal of this project is to design an electric motor configuration for the ChallengeX GM Equinox. An electric motor or motors will be selected as well as the best configuration to recharge the batteries as well as power the wheels of the vehicle. The all wheel drive configuration will have the front wheels driven by the electric motor and the rear wheels driven by the ICE (internal combustion engine). This means that a micro controller will have to be employed to make sure that the ICE and the electric motor turn the rear and front wheels at the same speed. In order to achieve this goal, certain technical and practical design constraints must be met.2.1 Technical Design ConstraintsThe list of technical design constraints is listed in Table 2.1. These constraints are product requirements that will give the best overall efficiency of the configuration. Table 2.1 – Technical Design ConstraintsName DescriptionHorsepower The output horsepower must be 100 hp ± 10%. System Management A micro controller will manage the electric motor’s input. The micro controller will regulate the input relative to the drivers input (i.e. the further the gas pedal is pressed the more voltage and current to the motor). The controller will need to output enough current for the electric motor to output the same mechanical power as the ICE.Regeneration The motor must regenerate the batteries while the vehicle is costing or when the vehicle is breaking.Strength The motor must withstand the extreme torque loads under extreme conditions.Efficiency The overall motor efficiency must be 75% or greater.2.1.1 HorsepowerIn order for our motor design to be beneficial to the Equinox, it must be highly efficient. When a load is applied to the motor, the motor must be able to apply enough horsepower in order to operate the vehicle properly. For the given vehicle design, in order to meet the criteria, the motor must deliver 100 horsepower ± 10%. 2.1.2 System ManagementThe electric motor will be placed in parallel with the ICE (internal combustion engine). The electric motor will split the responsibility of driving the vehicle with the ICE. The vehicle will utilize the all wheel drive configuration. All wheel drive was created to have better stability in harsh on road environments, not for off road environments. All wheel drive works on the same principles as part time four-wheel drive, but it is not equipped to handle high RPM situations. All wheel drives main purpose is to take power away from a wheel which is spinning and shift this power to the opposing wheel to provide better traction in harsh on road driving conditions. In order for our system to work the electric motor will have to power the front wheels. The ICE will provide power to the back two wheels. This is a majorconcern because the electric motor will have to provide the same exact power to the front wheel as the ICE provides to the back wheels. A micro-controlled speed controller will be employed to adjust the current and voltage to provide the same mechanical power to the front wheels as the back wheels. The driver’s foot will determine the voltage and current sent to the electric motor2.1.3 RegenerationThe electric motor designs all exhibit different regeneration characteristics. An electric motor that has good or excellent efficiency ratings will have a poor to average regeneration rating. The challenge of regeneration begins as a secondary trait of the motor, but is still extremely important. The motor must be able to regenerate the batteries in coasting and braking situations when it is not engaged and contributing to the acceleration of the vehicle. The switching to a regeneration mode must happen fast. This mode will not be the primary operation of the motor and therefore will have less time to accomplish its task of regenerating.2.1.4 StrengthThe weight of the vehicle will be supported by its suspension but the electric motor must still pull this weight from a complete stop. The electric motor must complement the diesel partner that will power the Equinox's rear wheels. In extreme cases of towing or climbing steep hills the electric motor must be able to handle the torque load that is placed on the motor. 2.1.5 Efficiency The overall efficiency of the electric system will depend on how efficient the electric motor operates under certain conditions. The overall efficiency of the motor configuration must be 75% or greater to exceed the efficiency of the original Equinox. 2.2 Practical Design ConstraintsThe practical design constraints of this project are shown in Table 2.2Table 2.2 – Practical Design ConstraintsType Name DescriptionEconomic Cost The cost of the motor must not be over $5,000.Manufacturability Size The motor must be approximately 19” x 12”.Manufacturability Weight The weight of the motor must be less than 800 lbs.Reliability Operating ConditionsThe motor must operate under foreseeable drivingconditions.Health and Safety Safety The motor must operate in a way that does notendanger the user. It should clearly indicatewhether or not the system is in operation.2.2.1 CostThe electric motor is a main component of the Equinox. The cost of the electric motor must not be so expensive, that it alone makes the vehicle unrealistic to produce. GM must be able to acquire the electric motor at a cost that is feasible for production. Therefore, the price of the motor must be less than five thousand dollars.2.2.2 Size The dimensions of the Equinox hood are approximately 58” x 36”. The diesel engine and the battery packmust also fit within this area. The diesel engine will take about half of this area, so that leaves approximately one half of the area for the electric motor and the battery pack. However, the motor will be connected, under the diesel engine, to the differential. This allows the motor to be approximately one thirdthe size of the given hood area, which is around 19” x 12”. 2.2.3 WeightThe weight of the motor plays a huge roll in the vehicular performance. A large amount of weight confined to one area of the vehicle may cause the vehicle to pull to one side while driving around corners or even going on a straight road. If a large confined weight is not centered in the vehicle, extra stress will be placed on other parts of the vehicle, thus, damaging them over time. Having a motor that is less than eight hundred pounds will allow the above side effects to be
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