Snowmobile Traction Control

Our goal is to implement a launch control (LC)/ traction control (TC) system on the 2016 Idaho Clean Snowmobile Team competition platform, modulated via an Electronic Throttle Control System (ETC). The components will be seated in a mechanical housing that can be implemented on a variety of platforms.

=Problem Statement=
 * To improve performance of previous year’s electronic throttle control (ETC) system
 * To implement an electronic launch control (ELC) system
 * To implement a traction control system (TCS)
 * Operate under CSC team time constraints

Background
Our main goal is to improve on the previous design with the addition of an electronic traction/launch control system. The previous year's design had an electronic throttle but the throttle action was delayed noticeably from the rider input. The previous electronic throttle raised some safety concerns with the delay in letting off the throttle. Our first priority was to improve the electronic throttle design to make it quicker and safer. Next, an electronic traction control and launch control system can be developed. Finally, the whole system will be packaged in a housing that in portable to other snowmobile models with minimal modifications.

Specifications

 * Traction control system allows the sled to travel a distance in less time than the stock platform.
 * Budget is $500 for Development and $200 for final system.
 * Throttle feel as close to stock as possible.
 * Use of a TI Tiva C microcontroller for processing system.
 * Reduce response time of Electronic Throttle Control system to half of the previous year's design. (< 150ms)
 * Operate under CSC team time constraints.

=Design=

ETC
An electronic throttle control system (ETC) on the competition platform developed by Idaho CSC was used as the basis for our design work. An ETC system is used on the competition platform to gain a greater level of control over input to the engine and to implement other control systems including launch control and traction control. To achieve the goal of a more responsive electronic throttle, we used a higher power, faster servo in place of the previous design. The servo chosen was a Savox 1257tg servo which has high performance for the price and also high quality titanium gears.

The performance gain over the old electronic throttle system using the new servo was substantial. The higher power servo also required a more capable power supply that needed to be designed.

Launch Control
The purpose of the launch control is to increase the average acceleration of the competition platform over a low traction surface from a stop. This is achieved by limiting the slip of the track which gives better grip and therefore better acceleration. The image below shows the sensor used to measure acceleration on the sled.

Electrical System
The electrical system for the sled has three main components:
 * Power Supply
 * Processing/sensors
 * Packaging/PCB

The first proposed design for the power supply included using parallel linear regulators to supply a fixed voltage while supplying the desired current. The concern with the parallel linear regulators is that they may not balance the current properly and fail. The next alternative was an off the shelf component that can supply the required current all in one package. This power supply required air flow which is unavailable in the package on the sled.

The design we selected was an LM2576 switching regulator with heat sinking capability.

The MCU chosen to process the sensor data and control the throttle position was the TI Tiva C Launchpad. This platform is already in use on other University of Idaho SAE teams so it was picked for this team for consistency and code portability.

Mechanical System
The mechanical system is made up of two major parts:
 * The throttle cable/false throttle body housing.
 * Servo/sensor/electrical housing.

The throttle feel is as close to stock as possible by using the stock cables and springs. The cables lead into a false throttle housing where the throttle position is sensed using a potentiometer. The false throttle housing is easily exchangeable between multiple platforms.

Implementation
The final product for the electronics on the sled are all packaged on one PCB board. This gives the electronics a more professional fit and finish than using a bread board. The PCB was designed in KiCad software. To keep the cost down, the PCB has to use only two copper layers and must be under 10cm X 10cm. The research for the trace sizes and via sizes was done using SaturnPCB software.

=Team Information=

=Document Archive= [[Media:team_contract.pdf]]

[[Media:sled_minutes.pdf]]

[[Media:lm2576data.pdf]]