High-performance EDA tools and electronics for formula racing

We are creating a system that collects data and shows whether the car is driving in accordance with IMechE safety rules. The system will allow designers to gain insight into vehicle dynamics to support future real-time design decisions for track fault detection, and use it in the form of recorded data for future reference. The data acquisition system should be portable and extensible so that it can accommodate multiple independent components of multiple vehicles or vehicles in the workplace or in the power laboratory (power meter).

With MulTIsim, we can simulate the entire connector and power distribution circuit of the vehicle before purchasing any component or PCB, thereby saving time and unnecessary costs. CompactRIO provides us with a robust, reprogrammable data logger that can receive input from multiple sensors. Using LabVIEW and a standard WiFi router, we have implemented a wireless telemetry system, which processes approximately 20 channels of analog data and 18 other channels of CAN bus data. Using LabVIEW, we can view the data in the correct format and create customized alarm signals.

The Formula Student Competition of the Society of Mechanical Engineers requires engineering students to conceive, design, manufacture and compete with small formula-style racing cars. After a year of construction, these cars were brought to Silverstone for judging and comparing with other competitors from all over the world. In 2008, 95 teams participated mainly in the vehicle category and low-emission vehicle category.
Virtual connector

The wiring simulation in MulTIsim allows us to check the operation of various safety circuit breakers to ensure that the system functions work in accordance with safety rules. We can simulate the current to evaluate the performance of the battery and optimize the PCB in UlTIBoard to handle those loads, especially the very wide lines used to start the motor current. Using mechanical CAD tools, we can ensure that our circuits will be encapsulated in the housing.
Data acquisition and telemetry

Auto frame, suspension, cooling and driving training are some important aspects, of which design verification based on real data analysis is very critical. Through simple simulation of CAD software packages, it is difficult to find weaknesses or areas to be optimized. The data is used not only in the design phase of the vehicle, but also in track adjustment in suspension and cooling systems.

CompactRIO provides us with an integrated data acquisition and real-time monitoring system, which has unparalleled flexibility in terms of input types and data viewing. 512 MB of on-board storage makes high-precision data capture possible. It provides a much higher channel density (the ratio of the number of input channels to the size) than most other solutions (even solutions specifically designed for sports motorcycles). Due to a simple WiFi connection, we don't even need to have an RF license for telemetry. Removable, wide-ranging C-series modules make CompactRIO a sustainable choice. We can change the configuration when our needs grow or when we discover new measurement areas. It also supports a wider operating voltage, which is very important for car power supply with frequent engine restarts (at this time the voltage drop may be as much as 25%).

We work closely with NI field engineers to tailor the hardware to suit our purposes. Our unit is an 8-module chassis equipped with NI 9237 synchronous bridge module, NI 9205 analog input module, NI 9411 digital input module, NI 9211 thermocouple module, NI 9233 dynamic signal acquisition module for IEPE measurement, and NI 9853 high-speed CAN input module. The CAN input allows us to monitor data from sensors connected to the ECU, such as RPM, gasoline temperature and gasoline pressure. This avoids repeated assembly of sensors or manufacturing sensor buffer circuits. The combination of rapid reprogramming and the portability of a single unit means that we can easily use CompactRIO in an automobile or power laboratory to obtain more detailed engine-related measurements. It only involves uploading the appropriate VI and sensor connections over the network.
On-site monitoring

The ability to monitor data in real time is very important to detect problems before they have serious consequences. During the test, the team can check whether the engine is at a constant temperature without stopping the vehicle. When the team is ready to change the suspension while the vehicle is still driving, the test session will be more productive, which means that the driver can gain more control practices.

Providing immediate feedback to drivers is also an effective way to improve their driving style. A good racer must always control his vehicle, just within the limits of traction. By observing the throttle position, brake pressure and steering wheel angle data during driving, a driver was informed of the aspects of his technology that needed improvement.
Vehicle dynamics

With linear and selective potentiometers, the vehicle's weight transfer characteristics can be observed in a quantifiable manner. By measuring the angle of suspension and steering, we can observe how the vehicle leans at the corner. The shock absorber can then be adjusted to minimize glide and increase grip.

When driving a racing car, it is important to observe the condition of the four wheels. We use a Hall sensor mounted on the upper right to measure the speed of each wheel. When the wheel turns, these sensors are triggered by a specially designed gear disc placed behind the brake disc. They provide a switching output compatible with transistor-transistor logic (TTL). Using the NI 9411 digital input module and a high-priority timed loop in LabVIEW, we can ensure that the sensor signal is sampled at a sufficiently high sampling rate. The wheel speed data and the expected direction data from the steering wheel angle sensor are used to understand and verify the work of the limited-slip differential, traction control, and starting control. The engine control unit (ECU) provides adjustment control for the last two items. We can find the best setting by measuring the wheel speed at the corner or when deviating from the starting line.

We use the NI 9237 bridge module to read the strain gauge readings placed on the suspension arm and the chassis tube. Although we can do very little work with this data on vehicles that have been built, this data will be very useful when designing future vehicles. For example, if the pressure on the component is lower than originally predicted, the component can be redesigned to reduce weight.

The NI 9233 module has four 24-bit simultaneous sampling inputs to support a simple 2-wire connection to the accelerometer. The lateral acceleration can be quantified and compared with different combinations of wheel camber and tire pressure. After obtaining these correct ways, our car can pass more urgent corners at a higher speed and at a higher speed.
to sum up

NI hardware and software support our open trials and rapid adoption, which is very important for the development of automobiles. The Formula Student team completes a new racing car every year (which is very similar to any professional racing team), so the ability to be "unpredictable" is critical. The vast majority of off-the-shelf automotive data loggers do not provide the extensive connectivity of CompactRIO, especially for passive sensors like strain gauges. The MAN09 race car, which is expected to be completed in July 2009, is our first vehicle with CompactRIO. The first batch of data will deepen our understanding of automotive design.

CompactRIO has been focused on future controllers and recording devices. Its FPGA-based operation will be very suitable for applications such as active guidance suspension systems, anti-lock braking and hybrid driving training management.

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