Mashari Alkhamisi
Name
BE 385
Dec 02, 2021 – Final Exam
Due Thursday, Dec. 07 @ 11:00 AM
Notes:
Turn your answers via D2L
Be brief and to the point, but clear and convincing
Sometimes all I am looking for is a “keyword” that succinctly captures the answer(s)
[15] GPS systems require a minimum of four satellites to get an accurate 3D position.
[5] Why a minimum of four and not three?
While one solution would often be impossible, three satellites provide two possible answers to a position. A fourth satellite aids in the elimination of one of the solutions, leaving only the most reasonable option. More of Four satellites aid in narrowing the answer to a single location and making communication between satellite and receiver easier. If Intersection of 3 satellites and take a look will show an error resulting. The intersection is never a singular point that could come to the patch area. if we add more satellites that middle area will shrink and narrow to almost a point.
[5] If more than four are available, what can you do with the additional satellites/signals?
We can narrow down the position to the average indicated/derived from all of the satellites if we have more than four. More often than not, more indicates the ability to minimize noise by averaging, and the location converges to the more exact point.
[5] Propose a mathematical approach for using these additional satellites/signals (think in simple terms)?
If we have at least 3 satellites it will let us know the location. We’ll have solutions for the location if we use more satellites. We must discover a way to combine them all in order to use them. From GPS show your approximate location.
[5] What is the difference between an open and closed-loop control system? Draw an example of both systems? By minimizing an error function, a closed Loop control system keeps track of its goal and changes itself to attain it. An open loop moves towards the objective based on some assumptions and beginning instructions without reviewing what happens in between, resulting in the possibility of missing the target entirely. A closed loop does the same thing, but it changes itself as it gets closer to the objective to guarantee we arrive at the correct location; it is guided by the goal. Both have their own set of applications.
[5] A PID controller is also known as:
Two-term controller
Three-term controller
Four-term controller
Proportional controller
[5] What is the minimum number of PID controllers a quadcopter flight controller (FC) needs to implement? There are three PID controllers in total, one for each axis (pitch, roll, and yaw), and nine parameters.
[5] What is/are the most critical sensor(s) on a drone? Why?The most important sensor is the gyroscope, which is commonly included in an IMU gyroscope. A gyroscope provides important orientation measurements, which are necessary for hovering at a constant level. Other sensors are important, but they aren’t as important as the gyroscope.
[5] What is a Gyroscope Offset and Drift? They result from what? and how to correct them? When the gyroscope is at rest, it records, measures, and senses an offset. There should be no angular change when it is at rest. The angles are calculated by integrating the Gyroscope angular rate over time. Noise and tiny measurement errors grow over time, forming a continuous error/trend that grows larger and larger.
[10] Below are roll readings from a Gyroscope during a short drone maneuver. The start angle was -10o (figure below). Compute and draw the drone’s final roll angle?
-10o
Horizontal (0o)
–
+
Gyro Rotational Rate (o/s)
Start Time (millisecond)
3.5
2018
-4.25
12018
-2.5
15018
0
19518
[15] “Trilateration” principles used by Global Positioning Systems (GPS) is a technique based on computing distances from known transmitters to find a 3D position. Apply the principles of trilateration to estimate the position of a receiver R(x, y) in a simple 2D Cartesian coordinate system. Your receiver R(x, y) sees three satellites GPS1, GPS2, and GPS3 that are at locations (15000, 15000), (-15000, 15000), and (0, 17500) respectively (in km) in this hypothetical 2D Cartesian system.
Your receiver (R) clock measures the following times to each GPS satellite:
GPS1: 73.85 milliseconds
GPS2: 49.38 milliseconds
GPS3: 45.80 milliseconds
Note: You can solve this analytically or use an online tool (I shared one with you in class) if you wish.
[10] Find the receiver R (x, y ) coordinates in km, assuming the speed of light is 300,000,000 m/s, and show all your work.
[5] Draw a diagram of the position of each GPS satellite and the receiver in this 2D Cartesian system.
[15] To implement a collision-avoidance system (forward direction only, figure below) we use an ultrasound sensor that measures distances to objects and a GPS to track the drone’s route.
Safe distance (D)
GPS/Drone Path distance
Ultrasound sensor
[5] Propose a block diagram that describes the logic of how your solution might work if the obstacle is stationary?
[5] What if the obstacle is moving towards the drone at a speed lower than that of the drone?
[5] What if the obstacle is moving towards the drone faster than the drone getaway speed?
[20] Below is a simple Flight controller Algorithm Code
A=0.98;
B=0.02;
Angle[1]=A*(Angle[1]+Gyro_Angle[1]*Delta_Time)+B*Acc_Angle[1];
System_Error=Angle[1]–Set_Point;
PID_p = Kp*System_Error;
PID_i = PID_i+Ki* System_Error;
PID_d=Kd*((System_Error-Previous_System_Error )/Delta_Time);
PID = PID_p + PID_i + PID_d;
Output_Left=Min_Throttle+PID;
Output_Right=Min_Throttle-PID;
if(Output_Right < 1000)
Output_Right = 1000;
if(Output_Right > 2000)
Output_Right =2000;
if(Output_Left < 1000)
Output_Left = 1000;
if(Output_Left > 2000)
Output_Left =2000;
left_prop.writeMicroseconds(Output_Left);
right_prop.writeMicroseconds(Output_Right);
Prev_System_Error = System_Error;
[5] Can you explain what this flight controller code is doing, be brief and clear?
[5] What are the A and B constants in the code?
[5] What are the 1000 and 2000 numbers?
[5] Is the red highlighted portion of the code needed? Why?
BE 385- Final Exam Fall 2021
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