Week 5: aR&D 1
The first advanced research and development topic our team worked on was Coasting vs. Power Braking. The objectives of this aR&D were understanding the difference between coasting and powerbraking and determining which works better with our teams AEV. Some different ways of breaking are shutting off the motors, reversing the motor direction and using the servo motor as a physical break. Our team experimented with shutting off the motors and reversing the motors to stop our AEV.
The code we used for coasting was:
rotateServo(45); //set servo to initial position
reverse(4); //reverse initial motor
motorSpeed(4,40); //set power to 40
goFor(3); //go for 3 seconds
brake(4); //stop
The code we used for power breaking was:
rotateServo(45); //set servo to initial position
reverse(4); //reverse initial motor
motorSpeed(4,40); //set power to 40
goFor(3); //go for 3 seconds
brake(4); //brake all motors
reverse(4); //reverse all motors
motorSpeed(4,50); //set to high speed to stop quickly
goFor(1); //go for under a sec
brake(4); // stop
As shown by Figure 1 below, the coasting uses less power, but takes longer to stop. Meanwhile reversing the motors uses a lot more power but stops about 0.5m sooner. Our team concluded that coasting is not very accurate and reversing the motors takes up too much power, so in our final design we will use servo breaking to give the AEV better stopping power.
Figure 1: Power vs. Distance Graph for Coasting vs. Power Breaking
Week 6: aR&D 2
The second aR&D our team worked on was Energy Analysis. The purpose of this aR&D was to calculate propellor and friction forces using samples of AEV data. The data collected allowed us to make comparisons between the different designs in class and help us improve our design. Our AEV weighs .303 kg with our 3D printed frame. In the first task, our AEV travelled 109.38 inches, which is equal to 2.78 meters or 227.0 marks. In the third task, our motors stopped after 4 seconds and our AEV stopped after 4.08 seconds. Our motor stopped after 114.0 marks (1.395 m) while our AEV stopped after 221.0 marks (2.705 m).
The AEV wheel count sensors measured the distance the AEV travelled at .4875 inches per mark. The initial Marks error was 6 marks. To reduce this error we made sure the sensors were connected and used a meter stick to make our measurements more precise. Our team concluded our AEV’s friction force as 2.642 N and propeller force to be 2.695 N using the equations provided.
The code we used for this aR&D was:
motorSpeed(4,30); //set speed of all motors to 30% power
goFor(4); //go for 4 seconds
motorSpeed(4,0); //set speed of all motors to 0% power
goFor(10); //go for 10 seconds
Week 7: aR&D 3
The third aR&D our team worked on was Servo Function. The objectives of this aR&D were to understand how a servo motor can be integrated into our AEV and to test its effectiveness. We decided to use the servo as a power brake to stop the wheels instantly. As shown here the difference between the servo motor and the coasting is less power used, and also a lot more controllable than the coasting method and uses a lot less power than power breaking. Our team concluded that to have the most precise and efficient AEV, the servo motor would be the way to go. There was a slight error in the graph because the power level for the servo brake is lower, but the outcome is still the same.
Figure 2: The Servo Motor Attached to our AEV
Figure 3: Power vs. Distance graph for Coasting, Power Breaking and Servo Breaking
Week 8: aR&D Oral Presentation
The goal of the aR&D oral presentation was to summarise the aR&Ds. Our team conducted 3 aR&Ds. We created a presentation covering the objectives or goals of the aR&Ds, their results, an analysis of their results, a conclusion we reached based on the results and how we would use the data collected to improve our final AEV design before the performance tests. Some of our delimitations, factors we could control, were the AEV’s structure and design, and the code we used to move our AEV.