Team NV11 Nanyang Autonomous Venture from NTU received the Vehicle Design Award for the Urban Concept category
Published on: 26-Jun-2020
Nanyang Technological University Venture 11, (NV-11) is a 4-wheeled, autonomous ready, battery powered electric vehicle. It has been designed and built by 2 NTU student teams in 2019 and 2020 respectively.
The vehicle is a two-seater including driver and passenger. Similar to a modern vehicle, it is equipped with 4 doors; the front pair is front hinged and the rear pair is rear hinged to allow for easy access.
Design of NV-11 started in the early 2018, to participate in the Shell Eco Marathon 2019 autonomous event. However, due to cancellation of the event, NV-11 was stripped off its autonomous equipment and participated as battery powered electric urban concept category. For the year of 2020, prior to its cancellation, NV-11 was to return to Shell Eco Marathon in the same category with further improvements and aims to surpass its predecessors.
This report summarizes the details about NV-11 vehicle; modifications and tests to optimise weight and performance efficiency. It will focus on the features as a SEM Urban category battery powered electric vehicle and not on the autonomous features.
Professor-in-Charge : Assoc Prof Ng Heong Wah (MAE)
NV 11 (2019) : Renny Lim (ME/4) , Zachary Chua (ME/2), Martias Try Wardhana (ME/4), Lim Shu Fang (REP/4), Le Bao Trung (ME/4), Tay Jun Yang Sherman (REP/4), Muhammad Azri (EEE/4), Pan Xin Min (EEE/2), Ng Ting Hao (REP/4), Shen Chen (REP/2), Orion Dai Yuhui (ADM/3)
NV 11 (2020) : Randy Wong Jia Cheng (ME/4), Peter Chong Ken Yang (ME/4), Bharat Krishnan (ME/4), Tan Hong Wee (ME/4), Feng Xiao Tian (ME/4), Tham Mun Chung (ME/4), Goh Jun Hao Daniel (EEE/4), Yeo Zhi Duo Darren (EEE/4)
Vehicle Concept & Styling
a. General Design
NV-11 is the 11th member of Nanyang Technological University’s vehicle family. As an Urban Concept Category vehicle, all the technical regulations have been satisfied. Moreover, the vehicle aims to be ergonomically comfortable and convenient to drive in and manoeuvre in city streets.
b. Vehicle Silhouette
An Orca whale’s body has a streamline body shaped that enable it to easily move under water. Because of its aerodynamic shape, it was decided to adopt this inspiration into the design of NV-11 vehicle.
With inspiration drawn from the profile of an Orca whale, the eyes and blowhole of the whale become a window, while the fins transform as wheels of the NV-11 vehicle as seen in figure 5.
c. Detailed Design of NV11
From the sketches, the body shape is created in Rhino modelling software for rendering and styling purpose. On passing the final acceptance, the Rhino model file is converted into Solidworks software for detail engineering. Note that the Rhino model is an empty shell, the Solidworks will add internal and external details which require the combined effort of 4 engineers. These details include; headlights, windows, ventilations vents, door hinges and latches, boot, bonnet and other autonomous features and mechanisms as shown in the figures below.
d. Vehicle photos
a. Vehicle Material Choice
Carbon composite material has been selected to build the shell of NV-11. Carbon composite is chosen due to its light weight, high stiffness and high tensile strength capabilities. To engineer the material for NV-11, 4 different carbon fibre and hybrid Kevlar fibrics were used in the construction. Seats are Kevlar/carbon while internal body layout are wide plain weave.
Kevlar and plain weave carbon fibre fabrics.
Utilizing the concept of a Sandwich Model, the fibres are weaved together with inter-stacking models laid at alternating directions as shown in figure 15 and 16. The thickness of the core ranging from 0 to 10mm as well as number of layers/directions of fibre are dynamically varies across the body. This reduces weight while acquiring sufficient vehicle strength.
The door, bootlid and bonnet hinges are made of Kevlar without any metal, as shown in figure 17 – 20. Due to its flexible capability and durability, it is able to withstand huge amount of manhandling while maintaining light weight and aesthetically appealing.
b. Body Structure
To make a body with high strength to weight ratio, the unibody or monocoque concept is implemented. A unibody consists of a fusion of both the chassis and body shell. The figure below shows the structural elements of the car.
The seats and bulkhead are assembled on top of structural beams to support the car’s roof in case of a roll over. This is also to isolate the passenger cabin from the boot (rear) and bonnet for the autonomous system (front).
Together with the carbon fibber body structures, energy can be absorbed during frontal impact, protecting drivers from any potential accident.
Overall, the total weight of the entire body shell and chassis construct amounts to 50kg. With the inclusion of all the systems (drive system, autonomous actuator, etc), the vehicle total weight contributes to 120kg.
c. Side Mirrors
The side mirrors have a unique retraction mechanism (rack & pinion) which allows the mirrors to adjust by extending and retracting as shown in figure 25 & 26.
When extended, fresh air is able to enter through the cabin vent, ventilating the cabin and exits at the rear openings.
During autonomous mode, the side mirrors are automatically retracted. This greatly reduces drag and improves efficiency while providing a flush exterior.
The mechanisms are 3D printed, enabling structure optimization, hence a light weight assembly.
To prevent the vehicle from overheating and improves the overall vehicle comfort, the NV-11 has 3 different independent ventilation paths for cooling; front air intake to cool front electric compartment (for EV electrical system), cabin vent intake to cool cabin and rear floor intake for rear electric compartment (for AV autonomous system). The outlets for the air are through the rear and floor pan outlets. If necessary, the air can be propelled by electric fans (not installed). Figure 27 depicts how the flow paths in the respective colour codes.
Aside from providing an aesthetic look, front air vents of a car are designed to allow airflow within the car to cool off electrical components; such as brake, accelerator and steering actuators and AV related electrical system and computers.
For the rear vent intake, air flow in through NACA ducts from the floor and exit through front and rear duct designs (blue & green path in fig.27).
d. Driver’s ergonomic consideration
Human factors are taken into consideration the comfort and seating position that provides maximum visibility for the driver; >200° field of sight (from side to front view). Ample space is provided to achieve 90th percentile size of average human as shown in figure 29 & 30.
All control and emergency switches are placed within immediate reach of the driver.
e. Emergency Safety
In an emergency, such as fire or lost in control of the vehicle, emergency stop switches are located at the steering wheel and at the rear of the vehicle as shown in figure 31 and 32. Once these emergency switches are engaged, the power will be cut off immediately causing the vehicle to come to a halt.
Vehicle Optimization and Modification
Streamline body design and efficiency
A simulation has been conducted to determine the drag and aerodynamic drag coefficient. By simulating the wind tunnel conditions, it is found the body frame is designed to reduce drag and enhances aerodynamic when the vehicle is moving. As shown in figure 33, the wind flow depicts the smooth flowing along with the body of the car.
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