Lead Architect: Ryan J. Richards
The Pennsylvania State University - School of Electrical Engineering and Computer Science
The linear actuator is used to control the steering angle of the snowmobile. A motor shield (attached to the main ArduinoMEGA) serves as a programmable switch between the Arduino and the actuator. Although a relay would be the simplest way to control the actuator, the actuator must be constantly switched on/off and move in different directions. Switching a relay too often significantly lowers the lifespan of the device. However, by using a motor shield with the Arduino, Pulse Width Modulation (PWM) can be used - which can be constantly switched without worry and has the programmatical ability to reverse the polarity of the power supplied to the actuator (which gives makes it either extend or retract).
LINX is a library developed by MakerHub that allows programmers to interface with the RaspberryPi, Arduino and other microcontrollers on LabVIEW. LINX has been used extensively in this project to communicate with the ArduinoMEGA, which controls each subsystem. Download and other information can be found at:
The actuator setup utilizes a motor shield [1] that attaches to the ArduinoMEGA. This shield is capable of controling two motors, however we will only need to control one. The motor shield has the following schematic:
Setup instructions:
(1) connect the External Power Jack to a power supply/battery with the appropriate voltage/current
(2) connect the M1+ jack to the positive terminal of the actuator
(3) connect the M1- jack to the negative terminal of the actuator
(4) attach the Motor Shield to the ArduinoMEGA - ensuring that the setup matches the pictures below:
The final setup should look like this:
This LabVIEW code exemplifies the basic control system for the actuator using the motor shield. The code used in the SnowDrone main VI uses this setup but separates the configuration slightly to accomodate the message-based architecture.
Setup and execution:
(1) set the PWM Channel to 9
(2) set the IN1 Channel to 8
(3) set the IN2 Channel to 11
(4) set the Duty Cycle to 1
(5) set the Serial Port to the COM port of the ArduinoMEGA
(6) Run the VI and press either the Extend or Retract button - the actuator will then extend/retract accordingly
(7) Press the Stop button when done (rather than aborting execution - this ensures that the Arduino connection is closed)
Mounting the actuator to the snowmobile is a very laborious task since there are very few mounting points on the snowmobile itself.
The 2015 PSU SnowDrone team sought to mount the actuator on a metal apparatus (which attached to the seat of the snowmobile) and connect the actuator to the steering handle itself. However, the steering handle did not move in a linear motion which means that this is not an optimal mounting position.
The 2017 PSU SnowDrone team sought to mount the actuator to the bottom of the snowmobile - one end connecting to the front sled steering connection itself while the other end connects to some fixed point on the snowmobile. This proved to be a hard but (semi) achievable task.
Propsed connection steps:
(1) connect the moveable end of the actuator to the right-sled steering base
(2) connect the fixed end of the actuator to bolt openning on the base of the snowmobile
Note: The fixed-point mounting is highly susceptible to movement and is not entirely secure - therefore a mounting reinforcement piece must be designed. The piece must attach to a stable location/set of points and be large enough to extend to the mounting point of interest.
Since the fixed point on the snowmobile was not a sturdy enough mounting position, a mounting bracket was designed in SolidWorks which reinforces the fixed point. The snowmobile's running board has secure holes where bolts can penetrate the metal and have a stable connection. The mounting bracket extends from the running board bolt holes to the actuator fixed point. The mounting bracket is thick and can be printed in tough PLA (plastic) - lightweight but still strong enough to support the actuator. The bracket has a specially designed hole which accomodates the actuator pin - a sturdy piece which goes into the actuator mounting hole (rather than using a thin screw), this is evidenced in the SolidWorks pictures below.
Note: All solidworks parts and the final mounting assembly can be downloaded from this GitHub repository.
(1) A new motor shield must be purchased since the power draw of the actuator is too large for the current motor shield and therefore will be severely limited in its pushing/pulling capabilities. The optimal choice for a new motor shield is: Motor Controller
(2) New mounting point for fixed side of actuator that will be secure enough to withstand the force of the actuator.